Why the ocean is becoming the next battlefield

December 2025

1. Abstract

Modern defence planning increasingly recognizes the undersea domain as a critical part of the multi-domain operating environment. What was once a niche domain reserved for nuclear deterrence and covert patrols is turning into a fully-fledged strategic battlespace, where geopolitical rivalry, economic resilience, and technological competition now intersect. As states race to protect 1.4 million kilometres of subsea cables, expanding offshore energy networks, and access to chokepoints, the undersea domain is moving from “out of sight” to “top of mind” for defence planners and governments.

NewSea is the new NewSpace” reflects how the maritime and underwater domain is undergoing a transformation similar to what space experienced over the past decade. Advanced maritime technologies are becoming more accessible and cost-effective, driven by autonomy, digitalisation, and IoT. Innovation is increasingly powered by strong public–private collaboration, with new entrants bringing fresh perspectives and scalable business models alongside traditional players. At the same time, investment patterns are shifting, with growing flows from venture capital, private equity, and public funding accelerating the development and commercialisation of new maritime and subsea capabilities.

At the same time, the traditional model built around a few exquisite, manned platforms is breaking. As they become more widespread, cheap and easy-to-deploy unmanned underwater vehicles could enable saturation tactics, covert infrastructure attacks, and novel forms of hybrid pressure that many naval forces are not yet fully prepared to address. The same dynamics that allowed low-cost surface drones to challenge major fleets in the Black Sea and the Red Sea are now migrating underwater, only this time in an opaque, GNSS-denied environment where detection is harder and attribution is ambiguous.

This paper explains why the next strategic revolution is happening underwater, and why it is happening now. It analyses the macro drivers (geopolitics, critical seabed infrastructure, and technology maturity), then maps the main military missions being reshaped: Battle Space Control (Mine Warfare, Anti-Submarine Warfare, Naval Combat), Infrastructure and Sovereignty Protection (Seabed Warfare, Maritime and Coastal Surveillance), Information Superiority (Undersea Signal Warfare), and Support, Rescue & Logistics. It then highlights the cross-cutting technology trends, miniaturised and attritable robotics, swarm autonomy, edge AI, resident systems, open architectures, and shows how a new generation of startups and scale-ups is redefining the underwater order of battle.

2. Strategic context and operational overview

The undersea domain, once perceived as a remote and silent extension of the maritime environment, has become one of the most contested and strategically decisive spaces of the 21st century. Formerly limited to nuclear deterrence and covert intelligence work, it has become a multidimensional space shaped by strategic, economic, and technological dynamics.

The undersea domain, once perceived as a remote and silent extension of the maritime environment, has become one of the most contested and strategically decisive spaces of the 21st century. Formerly limited to nuclear deterrence and covert intelligence work, it has become a multidimensional space shaped by strategic, economic, and technological dynamics.

For the first time, the seabed, the water column, and the surface form an integrated battlespace. Modern navies are no longer concerned solely with controlling the sea surface or projecting power through carrier groups: they must ensure continuous situational awareness across the full vertical spectrum of the ocean. This shift is driven not only by the resurgence of submarine competition, but also by the simple reality that our societies have quietly built a vast, fragile, and indispensable network under the waves.

Beneath the surface lies the world’s circulatory system:

• The global internet is carried by millions of kilometers of fiber optic cables,
• The backbone of energy interconnectors linking national grids,
• The fast-expanding infrastructure of the offshore wind industry,
• An emerging layer of autonomous sensors and resident underwater vehicles.

The ocean floor has therefore become a strategic asset in its own right, an invisible but vital infrastructure whose protection is now as essential as airspace or cyberspace defense.

In November 2024, two major subsea fiber-optic cables linking Northern Europe were severed in the Baltic Sea, the 218 km link between Lithuania and Sweden and the 1 200 km C-Lion 1 cable connecting Finland and Germany, in incidents widely suspected to be acts of sabotage. Governments quickly raised the alarm, calling the incidents a warning sign of hybrid threats targeting critical infrastructure underwater. Meanwhile, the sabotage of the gas pipelines Nord Stream 1 & 2 in 2022, where underwater blasts ruptured the conduits and caused major underwater explosions, demonstrated that energy infrastructure under the sea is as vulnerable as communications networks.

In parallel, the Indo-Pacific illustrates how undersea geography is becoming a strategic weapon in itself. China’s ability to deploy and protect its submarine force is constrained by the “first island chain” (Japan–Taiwan–Philippines), a set of closely monitored straits and relatively shallow seas that limit discreet access to the open Pacific for nuclear submarines. This is why deep-water gateways such as Taiwan’s eastern approaches and the Bashi Channel are so critical,and why Beijing has invested heavily in the South China Sea, particularly the Spratly Islands, where expanded infrastructure supports a more persistent military posture and helps secure access to deep underwater routes toward the Pacific and the Indian Ocean.

At the same time, the character of underwater operations is undergoing a profound transformation. The traditional model (few exquisite, extremely expensive, manned platforms) has reached its limits. Modern threats evolve faster than procurement cycles, and adversaries are increasingly ready to exploit asymmetries. The emergence of small, autonomous, low-cost underwater systems is challenging decades of naval doctrine. The transformation seen with USVs and aerial drones is increasingly driving ambitions underwater, where the development of cheap, resilient, and easy-to-deploy UUVs is intended to broaden the range of actors capable of operating below the surface.

This shift marks the beginning of a new strategic paradigm characterized by:

• Persistent presence enabled by autonomous fleets rather than manned patrol cycles
• Distributed sensing instead of point surveillance from a few high-value units
• Scalable mass through swarms rather than single exquisite platforms
• Machine-speed intelligence processing replacing manual acoustic analysis
• Rapid, modular innovation cycles inspired by commercial robotics rather than legacy shipbuilding timelines

The underwater environment is also becoming more transparent. In 2023, Norwegian authorities reported that an unidentified submarine operating off the coast had been detected not by traditional naval assets but by a network of passive seabed sensors installed to monitor offshore infrastructure. The incident illustrated how distributed sensing can now reveal platforms that once relied on deep-water opacity for concealment, a sign that deep ocean is becoming increasingly knowable. Advances in synthetic aperture sonar, passive acoustic processing, distributed sensing, quantum magnetometry, and underwater communications are progressively eroding the sanctuary that the deep ocean once offered. What used to be “the last opaque domain” is beginning to take shape as a data-rich operating space, one where real-time awareness is increasingly achievable.

Yet this new visibility also benefits adversaries. The wider availability of dual-use technologies (high-performance batteries, MEMS navigation, compact sonar, edge AI computing) means that underwater capabilities are no longer restricted to major powers. Non-state actors and mid-tier nations can now access operationally meaningful systems, creating an entirely new spectrum of threats that Western navies are not fully prepared to address.

In this context, underwater dominance can no longer be approached through incremental upgrades. It requires a redesign of how we patrol, sense, protect, deter, and intervene across the entire depth of the ocean. This article outlines why the strategic revolution is happening now, identifies the macro forces accelerating this shift, and examines how each military function (from Mine Countermeasures and Anti-Submarine Warfare to Seabed Protection and Undersea Signal Warfare) is being reshaped by autonomy, data, and distributed systems.

3. Macro Drivers: Why This Market Is Accelerating Now

Beyond the strategic implications, the underwater defense and security market is undergoing a quantitative stem change : global military and homeland security spending related to subsea capabilities is expected to reach $30-40 billion annually by the early 2030s, while the broader underwater robotics and sensing market could exceed $ 100 billion when including inspection, offshore energy and critical infrastructure protection.

The underwater domain is experiencing a structural acceleration driven by geopolitics, the expansion of critical seabed infrastructure, and the convergence of mature technologies. Over the longer term, the emergence of rustic, low-cost, and easy-to-deploy underwater drones, producible and deployable at scale, could introduce a new asymmetric challenge that current naval forces are not yet fully prepared to address Together, these forces are transforming underwater defense from a niche capability into a major strategic and industrial priority.

3.1 Geopolitical tension is driving states back underwater

A recent incident highlighted a direct confrontation between drones, when a Russian underwater drone was reportedly deployed against an unmanned Ukrainian naval system, illustrating the emergence of robotization in maritime combat. This episode, which has yet to be widely documented publicly, marks a symbolic turning point: underwater warfare is gradually becoming a battleground for autonomous systems, rather than just manned platforms.

Rising great-power competition and hybrid warfare have dramatically increased the strategic value of the subsurface. Submarine activity is at its highest level in decades, deliberate or ambiguous attacks against underwater infrastructure are increasing, and the advent of cheap underwater drones has lowered the barrier to offensive action. Recent conflicts have demonstrated that even simple maritime drones can inflict significant damage: the Ukrainian USV strikes on Sevastopol in 2023 and the repeated Houthi attacks in the Red Sea illustrate how rudimentary, low-cost systems can challenge major naval forces. Applied underwater, the same logic becomes even more destabilizing.

Opportunity

Persistent underwater surveillance, autonomous patrol grids, low-cost ASW sensors, and counter-UUV technologies. While governments are only beginning to adjust their budgets to this new vulnerability, concrete programmes are already emerging. At EU level, the Commission has launched a dedicated Action Plan on Cable Security and is backing it with targeted funding: the European Cybersecurity Competence Centre is issuing a first €10 million call under the Digital Europe Programme to establish Regional Cable Hubs, with a total of €21 million planned over the next three years for hubs that will monitor and detect threats to submarine cables using aggregated data and AI-based analysis. A further €10 million call will finance preparedness and stress-testing of critical infrastructure under the Cyber Solidarity Act. In parallel, 51 “Digital Global Gateways” projects worth €420 million have been funded under CEF Digital to improve submarine data cable connectivity and resilience. At national level, Denmark has earmarked about 4 billion Danish crowns (around $600 million) to build 26 naval vessels, drones and sonar systems specifically tasked with patrolling and monitoring undersea cables and pipelines in the Baltic Sea, illustrating how cable protection is starting to translate into hard defence spending Necessity: Move from episodic monitoring to 24/7 underwater domain awareness, and urgently develop C-UUV (Counter-Unmanned Underwater Vehicle) doctrines and systems.

3.2 Critical seabed infrastructure is expanding and increasingly vulnerable

The global economy is becoming more dependent on assets on the ocean floor, from communication cables to offshore energy networks. This creates both immense economic stakes and new strategic vulnerabilities.

• 1.4 million km of communication cables carry 99% of global data
• A few coordinated actions on subsea cables can cut entire countries off from internet connectivity or electrical power, and repair operations often require complex logistics that extend over several weeks to multiple months
• Offshore wind expansion will triple capacity by 2030, adding thousands of kilometers of new cables

Opportunity

Seabed monitoring robots, Distributed Acoustic Sensing (DAS), anomaly-detection AI. The European Union (EU), aware of the systemic nature of the threat, has put in place the EU Action Plan for the Security of Submarine Cables. This initiative aims to strengthen resilience in four main areas: prevention, detection, response and recovery, and deterrence. From 2025 to 2027, an additional €540 million will be allocated to strengthening digital infrastructure, in particular to securing submarine networks.

Necessity

Shift from periodic inspection to continuous integrity monitoring

3.3 Technology breakthroughs are unlocking new capabilities

Mature technological cycles (autonomy, sensing, energy, navigation) are removing barriers that historically limit underwater operations. Costs are dropping, endurance is rising, and intelligence is becoming automated.

• AUV deployments have increased 5× since 2018
• New battery technologies provide 30–50% more energy density
• AI-based sonar classification now reaches >95% accuracy in controlled environments
• The cost of producing a basic unmanned underwater drone has dropped to a fraction of traditional systems, enabling mass-deployment and swarming concepts

Opportunity

Affordable AUV/ROV platforms, swarm architectures, AI-native sensing, and counter-swarm technologies. At the same time, a clear price ladder has emerged: from ~$5k inspection ROVs such as BlueROV2, through “affordable” micro-AUVs like SEABER’s YUCO, up to sub-£1m small military UUVs like the REMUS 100M procured by the Royal Navy (£2.5m for three vehicles). This combination of longer endurance, AI-native sensing, and an order-of-magnitude drop in entry price is what makes scalable, distributed, and ultimately swarming concepts underwater technically and economically credible.

Necessity

Build scalable, distributed systems rather than relying on a few expensive assets, and develop defensive capabilities against cheap, proliferated underwater drones.

4. Key applications

4.1 Battle Space Control

Battle Space Control is the overarching strategic objective that governs direct military operations in the underwater domain. It represents the ability to detect, track, classify, and neutralize hostile forces and ordnance, that’s to say submarines, naval mines, and adversary Unmanned Underwater Vehicles (UUVs), surface and air targets.

In the subsea realm, Battle Space Control is inherently a challenge of denial and stealth. It is achieved by converting the opaque, high-noise underwater environment into a domain of persistent, predictable awareness through technological superiority.

The mission of Battle Space Control is addressed through three core use cases:

Mine Warfare                                Anti-Submarine Warfare                                     Naval Combat (MCM)                                                     (ASW)

The integration of these three disciplines ensures that the military can both neutralize immediate threats and guarantee the freedom of maneuver required to project power globally.

4.1.1 Mine Warfare

Mine Counter Measures (MCM) are undergoing a strategic resurgence driven by both historical legacy and contemporary conflict. European waters, in particular, face a constant threat from both the alarming quantity of unexploded ordnance from past conflicts and the new danger of deliberate sea mining. This ongoing cleanup, estimated at 2,000 to 2,500 explosive devices annually across Europe, is now compounded by current threats. The conflict in the Black Sea underscores this new reality and the current Russian conflict, where the use of floating mines severely threatens navigation and commerce in the region. This combined pressure necessitates a radical shift toward autonomous solutions to maintain the Freedom of Navigation in European strategic waters.

Europe’s response to this dual threat is a technological shift: moving away from the traditional “Man in the Minefield” approach toward “Stand-off” autonomous systems, keeping operators out of harm’s way.

This transformation is driven by a “toolbox” of autonomous systems…

• USVs (Unmanned Surface Vehicles): Platforms like Exail’s Inspector 125 act as communication relays and transport ships, deploying underwater robots while keeping
  the mothership safely away
• AUVs (Autonomous Underwater Vehicles): These are the core of detection. Equipped
  with SAS (Synthetic Aperture Sonar), they map the seabed with ultra-high resolution without human intervention.

Neutralization ROVs (Remotely Operated Vehicles): These are guided “Kamikaze” robots, such as Atlas Elektronik’s Seafox or Exail’s K-Ster C, designed to deliver and detonate a charge once a mine is identified.

Helped by European Programs and Collaborations

This technology is being standardized through major European programs:

rMCM (Replacement Mine Counter Measures)

is the flagship program for Belgium and the Netherlands. It is the first program in the world to fully rely on unmanned systems. It involves acquiring 12 new Motherships (City-class) and a “Toolbox” of over 100 drones, with the first ship, the M940 Oostende, launched and sea trials ongoing in 2025. Key industrialists are Naval Group (Ships) and Exail (Drones)

SLAM-F / MMCM (Maritime Mine Counter Measures)
is a Franco-UK program led by Thales and L3Harris, focusing on developing a prototype autonomous drone system (USV + Towed Sonar + ROV) to replace current minehunters. The transition to industrial production of the “Blue Class” fleet is underway

PESCO “MAS MCM”
is an EU initiative aiming to standardize this drone “Toolbox” across  European navies to ensure interoperability

4.1.2 Anti-Submarine Warfare

Anti-Submarine Warfare (ASW) has re-emerged as a core NATO priority due to the return
of a sophisticated Russian submarine threat. Modern platforms such as the Improved Kilo, one of the world’s quietest diesel-electric submarines, and the Yasen-class SSNs with long-range cruise missiles have driven a major Allied reinvestment in persistent ASW. This now relies on P-8A Poseidons deploying large sonobuoy fields, frigates like FREMM ASM and Type 23 towing CAPTAS-4 low-frequency sonars capable of detecting submarines at tens of nautical miles, and MH-60R helicopters using dipping sonars in shallow waters.

Operational focus remains on preventing incursions into key chokepoints such as the GIUK Gap and the Barents-to-Norway Bear Gap, NATO’s historic forward defense lines.

Evolving underwater threats:

ASW must contend with an increasing complexity of threats,
categorized into three main groups:

• Nuclear Attack Submarines (SSN/SSGN)
  Platforms like Russia’s Yasen-M class are now considered “peer
  competitors” to Western submersibles. They possess exceptional
  acoustic stealth and the capability to launch hypersonic missiles
  (Zircon) undetected from deep Atlantic waters
• Modern Conventional Submarines (SSK)
  Equipped with Air-Independent Propulsion (AIP), these diesel-electric submarines can remain submerged for weeks. They are smaller, cheaper, and crucially quieter in noisy littoral waters (like the Baltic Sea or the Strait of Sicily), making them extremely difficult
  to detect in tactically important zones
• Extra Large Unmanned Underwater Vehicles (XLUUVs)
  Represented by concepts like Poseidon or Surrogat, these large autonomous drones
  pose a new challenge. They can lie dormant on the seabed for months as “sleeper mines”
  or mobile sensor platforms, effectively bypassing traditional acoustic barriers

Technological Enablers

To ensure success against increasingly stealthy and persistent underwater threats, ASW relies on crucial technological advancements designed to operate autonomously in opaque and contested environments. These assets, required for continuous underwater awareness, can be deployed onboard surface or underwater drones, military vessels, or integrated into fixed infrastructure

This capability is sustained by three core pillars of innovation:

• First, Navigation & Positioning are essential for accurate tracking in environments
  where GNSS is unavailable or unreliable. Systems include MEMS-based INS/AHRS
  (Inertial Navigation Systems / Attitude and Heading Reference Systems)
• Then, Power & Endurance for long-duration and persistent missions. This is addressed by high-density Lithium-ion battery packs for AUV/ROV endurance, and fuel cell-based charging for fully autonomous resident operations
• Finally, Acoustic and Passive Sensing are the foundation of detection. This includes deploying advanced seabed sensor networks and towed arrays that utilize complex signal processing to discern faint submarine signatures from background noise

4.1.3 Naval Combat

Naval combat is undergoing a major shift from manned-centric doctrine toward fully integrated autonomous operations across subsurface, surface, and air domains. This evolution introduces new offensive and counter-capability challenges.

Air domain

Naval forces must also contend with drone swarms and advanced missiles capable
of saturating ship defenses. Managing simultaneous aerial threats has become a
core requirement of modern fleet protection.

Surface domain

Surface warfare now involves countering cheap, high-volume USVs that can threaten
billion-dollar naval assets. This growing cost asymmetry is pushing navies toward
more automated, AI-enabled Anti-Surface Warfare (ASuW) systems able to counter
both manned and unmanned threats at scale.

Subsurface domain

Armed UUVs and XLUUVs are transforming underwater combat by threatening hostile
drones, small submersibles, and critical seabed installations. Their rapid proliferation
is driving doctrine change, with the military UUV market projected to surpass $8B.
by 2030.

Solutions and Key Technologies

Counter-UUV (C-UUV) Systems: The development of specialized autonomous systems
for hunting and neutralizing enemy drones is paramount. These systems must combine high speed, acoustic stealth for approach, and tailored payloads (whether kinetic neutralization
or non-lethal effects)

Onboard AI and Autonomy: Artificial Intelligence is crucial for allowing combat drones
to make rapid tactical decisions, autonomously engage targets, and operate in coordinated groups (swarms) without requiring constant communication with the surface

Modular Subsea Weaponry: The miniaturization of payloads and the development of weapon systems specifically designed for the underwater environment and smaller platforms (lightweight torpedoes, precision charges) allow AUVs and XLUUVs to be effectively armed for
combat missions

Multi-Domain Coordination: Utilizing intelligent, interconnected platforms to manage and respond to surface threats, ensuring the efficient use of limited high-value munitions against swarming, low-cost targets

Robust AAW Capacity: Naval platforms require robust capacity to protect high-value
assets, engaging incoming aerial threats at multiple ranges, from long-range interceptors
to close-in weapons systems (CIWS)

4.1.4 Market challenges

Battle Space Control is about turning the underwater domain, naturally opaque, noisy, and favorable to stealth, into a space of continuous, predictable awareness. The first major stake is early detection: identifying submarines, mines, and unmanned systems before they can threaten naval forces, maritime trade routes, or critical infrastructure. Control of chokepoints such as the GIUK Gap or the Bear Gap is essential, as these areas determine whether adversarial submarines can enter the Atlantic or approach European coastlines unnoticed.

Another central stake is the protection of the seabed, where Europe’s digital and energy lifelines lie. Subsea cables, pipelines, interconnectors and offshore wind farms are now strategic targets, and their disruption could have immediate military and economic consequences.

Finally, Battle Space Control must counter the proliferation of low-cost autonomous systems, UUVs, drifting mines, and seabed-deployed sensors, that can saturate defenses and undermine traditional naval superiority. Achieving control therefore requires integrating advanced sensing, autonomy, and multi-domain coordination to ensure freedom of maneuver and credible deterrence in an increasingly contested maritime environment.

4.2 Infrastructure and Sovereignty Protection

• The strategic objective of Protection and Surveillance shifts the focus from direct kinetic engagement to persistent monitoring, intelligence gathering, and non-kinetic defense
• This discipline is fundamental to maintaining stability in the blue economy, safeguarding national borders, and ensuring the resilience of critical infrastructure against a spectrum of threats from sabotage and espionage to organized crime and environmental damage
• Protection and surveillance effort is executed across two primary functional areas, all relying on continuous Maritime Domain Awareness (MDA)

4.2.1 Seabed Warfare

Seabed Warfare has become a paramount strategic priority due to the world’s critical dependence on subsea infrastructure. The global economy and internet traffic rely heavily on a worldwide network of 1.4 million kilometers of active submarine cables (both optical and power). Europe, in particular, acts as the world’s most connected hub, serving as the main landing point for a significant share of these cables.

While most subsea cable failures remain accidental (over 80% caused by anchors or trawling, and around 15% by natural events), recent incidents have made the threat of deliberate sabotage explicit. The Finland–Estonia cable damage in the Baltic Sea is a prime example: investigators linked the break to a Russian-associated vessel whose drifting anchor likely severed the line, raising strong suspicions of intentional interference. The episodeheightened European concern over the security of undersea cables, power links, and pipelines, reinforcing the need for better surveillance, attribution, and coordinated protection acrossBaltic and NATO states. Globally, these networks still experience 150 to 200 outages per year.

Threats and Financial Implications

The stakes are not just security-related, but also financial and economic. The repair cost for a submarine cable is substantial, ranging from $500,000 to $1 million per incident for optic fiber cables, and potentially reaching $10 million to $100 million for power cables. For instance, the repair of the EstLink 2 power cable (Finland-Estonia) in 2024 was estimated at €50-60 million due to complex logistical requirements.

In light of these risks, the threat is twofold:

Offensive Threat                       

Dedicated platforms are being developed, such as China’s new deep-sea device reportedly capable of cutting undersea cables at depths of 4,000 meters (announced March 2025).

Intrusion and Espionage Threat
The need to protect cables against unauthorized taping and surveillance is constant.
In response to these growing threats, the European Union introduced an Action Plan on
Cable Security in February 2025 aimed at prevention and early detection

Technological Defense and Surveillance

• Fixed Sensing Systems:
  Distributed Acoustic Sensing (DAS) allows the fiber optic cable itself to be turned into a sensor. By shooting laser pulses through a “dark fiber” in the cable, operators can detect real-time vibrations along the entire line, signaling anchor dragging or a submarine landing
• Autonomous Surveillance:
  Patrols using AUVs and USVs are essential. Systems like the Saab Sabertooth (roving resident robot) or Exail’s Inspector 125 (surface drone towing a sonar) map the seabed to identify “foreign objects” added since the last survey. Long-endurance systems like the ARV-i from Boxfish Robotics, capable of staying submerged for months, are pushing the limits of persistent monitoring
• Surface Surveillance:
  Gap-Filling Radars are utilized along the coast to detect “Dark Ships” (vessels with AIS turned off) loitering suspiciously near cable routes

4.2.2 Maritime and Coastal Surveillance

Maritime and Coastal Surveillance is crucial for territorial integrity and economic security, especially considering that the EU and associated European states collectively control coastlines spanning roughly 70,000 km across the Atlantic, North Sea, Baltic, Mediterranean, and Black Sea. This extensive length drives the demand for persistent, long-range surveillance assets. The primary challenge is simultaneously managing legal commerce and detecting anomalous or illicit activities such as smuggling, illegal fishing, and maritime terrorism, all while securing critical port areas, littoral infrastructure and the safe departure of sensitive vessels.

The core motivation is to achieve comprehensive situational awareness from open waters down to dense coastal environments, effectively combating asymmetric threats that often hide in near-shore complexity.

Key Technologies and Surveillance Architectures

Surveillance relies on the integration of surface, air, and subsurface technologies to create continuous coverage and combat threats that bypass conventional surface patrols:

• Passive and Persistent Platforms:
  Gliders are a cornerstone of long-term maritime surveillance. These autonomous underwater vehicles (AUVs) operate passively, drawing energy from changes in buoyancy, allowing them to stay deployed for 3 to 6 months without recharging and travel thousands of kilometers to collect environmental, acoustic, and optical data.
• Detection Systems:
  

Diver Detection Sonars (DDS):

Essential for securing ports, naval bases, and critical infrastructure against underwater intrusion by divers or small submersibles. Companies like NORBIT Subsea contribute with specialized intruder detection solutions (GuardPoint)

Coastal Radars & AI:
Long-range coastal radar chains, increasingly enhanced by AI-driven detection
algorithms, are used to track surface vessels, particularly “Dark Ships”

Distributed Acoustic Sensing (DAS):

While primarily used for Seabed Warfare, DAS systems also contribute to coastal surveillance by turning nearby communication cables into vast acoustic sensor arrays

• Imaging and Intervention:
  For close-range inspection, robust underwater lighting systems provided by
  companies like BIRNS (US) are essential for detailed visual imaging in challenging,
  turbid environments

European Programs and Collaboration

European nations are standardizing and integrating surveillance efforts across the continent through multinational initiatives:

NATO “Baltic Sentry”

This program integrates aircraft, ships, and naval drones to enhance surveillance and security, particularly in the strategically sensitive Baltic Sea

EU CIP (Critical Infra Protection)

Focused on developing standardized capabilities and protocols to protect critical European infrastructure against various threats

SeaSEC (Seabed Security Experimentation Centre)

Acts as a collaborative hub for testing and refining new sensor technologies and autonomous platforms relevant to long-term surveillance

UK RFA Proteus

Represents a new class of operational assets. A vessel equipped with advanced

monitoring systems and submersible drones that is dedicated to enhancing maritime domain awareness and critical infrastructure protection

4.2.3 Market challenges

The market for seabed protection and maritime surveillance is constrained by three structural challenges. First, the cost–capability imbalance: while threats are becoming cheaper (UUVs, dark ships, hybrid sabotage), effective detection and attribution still require high-end, expensive systems (AUVs, SAS payloads, DAS networks). Customers are therefore unable to scale coverage to match the persistence of the threat. Second, fragmented governance and procurement slow adoption. Responsibility for subsea infrastructure protection is split between navies, telecom operators, energy companies, and EU institutions, resulting in uneven budgets, unclear ownership of sensors, and limited interoperability. Third, technological fragmentation persists across sensors, platforms, and command-and-control systems, making real-time Maritime Domain Awareness difficult to achieve despite increasing sensor availability.

These challenges create a widening capability gap: states cannot monitor all cable routes or littoral areas continuously, incident attribution takes days instead of minutes, and response options remain limited and reactive. Procurement cycles lag behind a threat environment where “cheap and numerous” replaces “rare and exquisite.”

4.3 Information Superiority Underwater

4.3.1 Undersea Signal Warfare

Undersea Signal Warfare (USW) is the subsurface equivalent of Electronic Warfare (EW). It has become a core discipline of intelligence and naval combat because it offers a decisive tactical advantage in the underwater domain, which is characterized by secrecy and opacity. Unlike Anti-Submarine Warfare, which focuses on kinetic detection, USW is centered on information and influence.

The strategic goal is to master the contested acoustic environment to map adversary capabilities, intercept discreet exchanges, and ensure the stealth and survival of one’s own submarines and next-generation autonomous platforms. This capability is vital for maintaining tactical superiority and deep-sea deterrence.

USW is executed through a continuous, multi-phased process that enables submarines and naval assets to maintain tactical advantage:

Collecting Underwater Signals (ISR)

Submarines use sophisticated hydrophones and sonar systems to passively detect and record acoustic emissions. These signals originate from a wide range of sources, including:

• Adversary surface vessels and other submarines
  (e.g., machinery noise, propeller cavitation)
• Underwater sensor networks and fixed monitoring arrays
• Covert acoustic communications between platforms.
  The goal is to build a detailed library of signal signatures for identification and tracking

Analyzing and Mapping Adversary Networks

Once collected, signals are analyzed using advanced algorithms, increasingly supported by AI/ML. This analysis allows military forces to:

• Classify Emitters: Identify the specific type and platform emitting the signal
• Map Sensor Networks: Determine the location, coverage, and operational patterns of adversary acoustic and communication sensors
• Intercept Communications: Gain intelligence by listening to and decoding covert underwater exchanges, which are challenging to achieve due to the environment’s inherent limitations on traditional radio waves

4.3.2 Market Challenges

Influencing the Acoustic Environment (Countermeasures)

The intelligence gained from collection and analysis is used to deploy acoustic countermeasures that disrupt or deceive the adversary’s efforts, analogous to the Electronic Countermeasures (ECM) used against radar:

• Active Decoys: Deploying devices that mimic the acoustic signature of a friendly submarine to draw away torpedoes or surveillance
• Noise Generation: Using specialized equipment to generate noise intended to mask the submarine’s own signature, often by operating at a similar frequency to the enemy’s passive sonar
• Acoustic Jamming: Actively transmitting signals to corrupt the data received by an adversary’s passive or active sonar systems, thereby denying them accurate targeting or detection

Undersea Signal Warfare faces several structural barriers that limit both adoption and scalability. First, the acoustic domain is inherently data-poor and environment-dependent: signal propagation varies with temperature, salinity, depth and seabed composition, making it extremely difficult to build universal, reusable datasets. This severely constrains the training of AI/ML models and slows the transition from experimental prototypes to operational systems. Second, access to real-world acoustic signatures is tightly controlled, as they are among the most sensitive military secrets. This prevents startups and emerging players from testing or validating solutions at scale, reinforcing the dominance of legacy primes with exclusive access to classified data. Third, platform integration remains complex and costly: USW systems must operate across submarines, AUVs, seabed sensors and surface assets, all of which use different architectures, security constraints and acoustic payloads, creating long and expensive integration cycles.

These challenges limit the pace at which navies can detect, classify and counter new underwater signatures. Operational commanders face longer attribution timelines, reduced confidence in automated classification, and difficulty maintaining stealth as adversaries deploy increasingly advanced sensors and networks. The result is a widening gap between the complexity of the acoustic environment and the tools available to understand and dominate it.

4.4 Support, rescue & logistics

4.4.1 Search and rescue

Underwater Search and Rescue (SAR) is being transformed by autonomous systems, which enable faster, safer intervention in an environment traditionally limited by poor visibility, slow mobilisation, and diver risk. SAR is now also strategic: recovering downed military platforms has become a race for sensitive technologies, as demonstrated by the F-35 crashes in the Mediterranean and South China Sea. With growing offshore infrastructure and more incidents at sea, autonomous platforms provide the only scalable way to ensure rapid and effective deep-water recovery.

A New Paradigm: Autonomous, Fast-Response Underwater Intervention

Modern SAR operations are shifting from diver-led missions to robotic-first responses, where unmanned systems handle the most dangerous and time-critical phases. Three drivers define this new paradigm:

Speed as a Strategic Imperative

Time is now the dominant variable in SAR, whether the objective is to save lives or secure a crashed high-value asset before adversaries do. Unmanned AUVs equipped with multibeam sonar and SAS can be launched within minutes, rapidly map debris fields, and operate in low visibility or hazardous waters.

Safety Through Robotic Intervention

Hybrid AUV/ROV systems can now operate safely in environments too dangerous or confined for human divers, including areas with collapsed structures, strong currents, or chemical contamination. They provide close inspection, object identification, and manipulation without exposing personnel to risk.

Persistence Beyond Human Limits

Long-endurance AUVs, gliders, and resident seabed systems allow continuous search
over vast areas or at extreme depths, far exceeding human endurance or ROV tether limits. Together, these capabilities make autonomous systems the backbone of fast, safe, and strategically decisive underwater SAR.

Key Technologies Reshaping Underwater SAR

SAR is increasingly powered by commercial-off-the-shelf technologies originally developed for inspection, mine warfare, or scientific research. Core enablers include:

• High-Resolution Sonar & Subsea Imaging
  Multibeam echosounders, Side Scan Sonar, interferometric systems, and SAS enable detection and mapping even in turbidity or total darkness.
• Hybrid ROV/AUV Architectures
  Vehicles that can autonomously navigate long distances and then switch to ROV mode for close intervention offer unmatched flexibility (e.g., Boxfish ARV-i, Tethys ONE).
• Autonomous Navigation in Zero-Visibility
  DVL, MEMS-INS, LBL/USBL systems and AI-based navigation allow stable flight in confined spaces—essential for interior wreck inspection.
• 3D Reconstruction & Digital Twins
  Ultra-compact 3D sensors (e.g., Tortuga XP4) provide millimeter-level reconstruction of wrecks or collapsed structures for planning extraction operations.
• Edge AI for Real-Time Classification
  Onboard processing shortens the cycle between detection, identification, and decision-making, especially in highly cluttered environments.

Strategic Impact: Why SAR Is a Sovereignty Issue

While SAR is deeply humanitarian, it also carries strategic and political weight:

• Rapid response capability reinforces national credibility and trust among allies
• Civil-military dual-use assets strengthen resilience across infrastructure, commercial shipping, and offshore energy
• Search operations near contested areas (Arctic, Mediterranean, Black Sea, Indo-Pacific chokepoints) have geopolitical significance, especially when high-end assets such as stealth aircraft are involved
• SAR missions provide invaluable data for bathymetry, environmental monitoring, and maritime security
• In crises, natural disasters, ferry accidents, aircraft losses, states are judged on their ability to act fast, decisively, and safely. Autonomous underwater systems provide the persistent, flexible, and scalable toolkit required to meet these expectations.

4.4.2 Support and logistics operations

Support and logistics operations form the hidden backbone of underwater warfare.
Modern undersea operations require platforms to be launched, recovered, recharged, maintained, repositioned, and resupplied, often far from ports and in contested environments. The emergence of resident AUVs, swarming concepts, and distributed sensor grids has accelerated the need for autonomous support infrastructure that can match this new operational tempo.

From Episodic Missions to Continuous Presence

Traditional underwater missions were defined by short deployments followed by long port-based servicing cycles. Autonomy has reversed this logic.

Persistent presence now requires:

• Forward-deployed launch and recovery points
• At-sea recharging and data offload nodes
• Automated health monitoring and fault recovery
• Low-signature logistics that do not reveal operations

This shift makes underwater logistics a decisive enabler of Operational Tempo (OPTEMPO) and mission persistence across the seabed, the water column, and the surface.

Key Functions of Modern Undersea Logistics

Launch & Recovery in Challenging Conditions

Unmanned Surface Vehicles (USVs) increasingly act as mobile logistics hubs, deploying and retrieving AUVs far from the mothership. They enable:

• Silent insertion of AUVs into contested zones
• Recovery in high sea states without putting crew at risk
• “Mothership-less” operations, ideal for covert missions

Recharging, Refueling, and Maintenance at Sea

Endurance is the main bottleneck for autonomous underwater forces.
New solutions are emerging:

• Subsea charging stations (e.g., Teledyne Marine’s Subsea Supercharger)
• Resident docking nodes for long-duration AUVs
• USV-based battery swap modules
• Modular mission bays for rapid payload changes

Data Retrieval and Mission Re-Tasking

Underwater comms are bandwidth-limited, making data logistics as importantas energy logistics. Support systems provide:

• Physical data offload through docking nodes
• Local processing “on the edge” to shorten turnaround time
• Remote retasking of AUVs via USV gateways or acoustic networks

Transport and Positioning of Swarms and Sensor Grids

Future underwater warfare relies on mass, distribution, and redundancy. Logistical systems must therefore support:

• Deploying dozens of small AUVs or sonobuoys in precise patterns
• Installing seabed sensor nodes across chokepoints
• Repositioning distributed networks as threats evolve

This capability is a key enabler of deterrence and persistent domain control.

Heavy Undersea Lifting and Recovery
For large objects (subsea infrastructure components, downed drones, or wreckage) heavy-duty work-class ROVs and specialized AUVs perform:

• Tethered lifting
• Precision alignment
• Component replacement
• Emergency recovery

These missions are essential not only for military readiness but also for maintaining
the resilience of energy and cable networks.

4.4.3 Market challenges

Search & Rescue and underwater support/logistics operations face a core challenge:

They still rely heavily on slow-to-mobilise, manpower-intensive systems, while the demand for rapid intervention in deeper, more remote waters continues to grow. Most SAR missions and maintenance operations depend on crewed vessels and complex ROV setups, which limits reactivity and makes it difficult to respond quickly to accidents, recover sensitive assets, or sustain operations far from ports.

A second challenge is the lack of standardisation and persistent support infrastructure.

Autonomous platforms remain constrained by battery life, limited at-sea charging options, and fragmented communication or navigation architectures. Without interoperable systems and reliable logistics nodes, USV hubs, docking stations, automated maintenance, autonomous fleets cannot maintain continuous presence or scale effectively. This creates a capability gap that industry can address by delivering lighter, more persistent, and interoperable solutions that reduce logistical burden and enable faster, more resilient operations.

Astal surveillance

5. Cross-cutting Technology Trends

Across Mine Warfare, Anti-Submarine Warfare, Naval Combat and Undersea Signal Warfare, a common set of technology trends is reshaping how military forces operate below the surface. These trends are less about individual “gadgets” and more about building mass, persistence and intelligence into the underwater battlespace.

5.1 Miniaturised and Attritable Underwater Robotics

Underwater robotics is moving away from a small number of large, exquisite vehicles toward many small, expendable platforms. Micro-AUVs under 5–10 kg, which can be launched from RHIBs, helicopters or even hand-thrown from the pier, are becoming tactically relevant tools.

In a military context, these micro-systems are used to:

• Probe and sanitize constrained areas (harbours, channels, under-pier spaces)
  before the entry of high-value units
• Conduct close-in mine reconnaissance in high-risk zones where losing
  the vehicle is acceptable
• Deploy as decoys or sacrificial sensors to trigger adversary responses and
  reveal their positions

The key point is that these platforms are rustic, easy to deploy and cheap enough to be attritable. They enable new concepts of operation based on saturation, where dozens of small robots can be risked to protect a single frigate or submarine.

5.2 Modular Payload and Effector Ecosystems

The underwater battlespace is shifting toward standardised “drone buses” carrying
mission-specific payloads. Rather than designing a new vehicle for every role, navies aim to field a small number of platform families and a large catalogue of plug-and-play modules.

Typical military payloads include:

• Sonar pods (SAS, side-scan, multibeam) for MCM and ASW.
• Electronic and acoustic intelligence packages for Undersea Signal Warfare (USW).
• Lightweight torpedoes, demolition charges or non-lethal effectors for C-UUV and precision strikes.
• Navigation and comms kits (INS, DVL, USBL/LBL, acoustic modems) that can be scaled to mission needs.

This modular approach enables:

• Rapid reconfiguration of the same AUV class from MCM to ASW support or USW collection.
• Shorter innovation cycles, where new payloads can be tested and fielded without redesigning the host platform.

5.3 Edge AI and On-board Processing

The underwater environment does not allow permanent high-bandwidth connectivity.
This forces a shift from “send all data to the ship” to “think on the edge”: most of the intelligence processing must happen directly on the drone.

Core trends:

• On-board classification of mines, contacts and anomalies,
  reducing operator workload and latency.
• Embedded tactical decision-making, where AUVs and USVs adapt search patterns,
  revisit suspicious contacts or collaborate with peers without waiting for human input.
• AI-driven acoustic and signal processing, essential for Undersea Signal Warfare
  and advanced ASW.

For Battle Space Control, this means that underwater assets are becoming autonomous teammates rather than remote sensors, capable of contributing to the tactical picture in near real time.

5.4 Swarm Robotics and Collaborative Autonomy

Swarm concepts are moving from theory to experimentation. The aim is to use groups of cooperating underwater drones to achieve effects that a single vehicle cannot deliver.

In the military domain, swarms enable:

• Wide-area mine hunting, where multiple AUVs share coverage
  and classification tasks to clear large zones faster.
• Multi-static ASW, with several AUVs acting as distributed sources
  and receivers to track quiet submarines from different angles.

Saturation and deception operations, where expendable drones force the adversary to reveal sensors, consume ammunition or defend multiple axes at once.

The long-term doctrinal question is clear: with an attritable swarm, it becomes technically and economically feasible to overwhelm a high-value asset such as a frigate, while current navies still lack mature, layered defences against underwater swarming attacks.

5.5 Open Architectures and the Rise of System-of-Systems Underwater Warfare

A major shift across all underwater military applications is the move from isolated platforms to open, interoperable, system-of-systems architectures. The goal is no longer to deploy a single “perfect” vehicle, but to orchestrate a heterogeneous force of USVs, AUVs, ROVs, seabed sensors and manned assets into a coherent, adaptive combat network.

This transition is driven by several imperatives:

System-of-Systems Integration

The undersea battlespace is now treated as a distributed combat cloud, where multiple assets collaborate, share dataand execute complementary roles:

• USVs act as gateway nodes
  (communications, launch & recovery).
• AUVs act as forward sensors or effectors.
• Seabed nodes act as persistent, low-signature ISR points.
• Manned vessels act as C3 hubs and host higher-level processing.

This architecture supports real multi-static sonar, collaborative ASW, coordinated MCM, and distributed C-UUV operations.

Open Software & Autonomy Ecosystems

The most profound “open architecture” shift is actually software:

• Containerised autonomy stacks that can be pushed to different vehicles.
• API-based command & control allowing multiple asset types to be piloted from the same console.
• Edge AI modules that can be updated or swapped like apps.
• Digital twins and simulation frameworks enabling rapid mission rehearsal and swarm optimisation.

This creates an underwater equivalent of the “combat cloud”, allowing rapid evolution of capability.

5.6 Resident Systems and Underwater Logistics

Finally, a growing trend is the move toward resident underwater systems: platforms that remain on the seabed or in the water column for months, supported by local docking and recharging infrastructure.

In a military context, resident systems are used to:

• Maintain continuous surveillance over key areas (approaches to naval bases, strategic cables, chokepoints).
• Provide forward-deployed launch points for MCM or C-UUV missions
  without exposing major surface vessels.
• Act as pre-positioned sensor or effector nodes that can be activated rapidly in crisis.

This creates a new layer of persistent, pre-positioned military presence under the sea, complementing submarines and surface fleets.

5.7 New Materials and Silent Propulsion for Stealth and Survivability

Stealth remains the fundamental currency of underwater warfare. New materials and propulsion systems are designed to reduce acoustic, magnetic and hydrodynamic signatures, directly increasing survivability in a dense sensor environment.

Key military-oriented trends include:

• Soft-robotics structures and biomimetic fins that mimic the movement of fish,
  generating far less cavitation than conventional propellers.
• Low-noise pump-jet thrusters optimised for slow, covert transit in littoral waters.
• Non-metallic or composite hulls that reduce magnetic signatures and make platforms harder to detect with MAD (Magnetic Anomaly Detection) and certain mine fuzes.

These advances are critical for:

• Covert insertion of AUVs into hostile areas for ISR, mine reconnaissance
  or cable surveillance in a contested context.
• Survivable C-UUV platforms that must approach enemy drones unnoticed
  to neutralise them.

5.8 Navigation, Networking and GNSS-Denied Operations

Underwater warfare is, by nature, a GNSS-denied environment. Accurate navigation and resilient communications are therefore central to all applications.

Key developments include:

• High-performance MEMS-INS and DVL combinations giving metre-level dead-reckoning over tactically relevant distances.
• Cooperative navigation, where swarms and mixed groups (USV + AUV) mutually refine their positions.
• Robust acoustic communications and covert low-probability-of-intercept (LPI) links, supporting USW, coordinated ASW and multi-vehicle MCM.

These technologies are enablers for:

• Long-range autonomous patrols in chokepoints and strategic straits.
• Complex, multi-asset missions where several vehicles must maintain a shared tactical picture under the surface.

5.9 Low-Cost, Attritable and Expendable Underwater Systems

One of the most disruptive trends in underwater warfare is the shift toward cheap,
consumable, and attritable systems. Navies historically relied on a handful of high-value, high-survivability platforms (frigates, submarines, dedicated minehunters). The emergence of rustic, simple, low-cost underwater drones radically changes this balance.

Why it matters militarily

Underwater saturation is now possible.

Small, inexpensive AUVs — sometimes costing 1/50th or 1/100th of a torpedo,
and far less than a frigate — can be manufactured and deployed in numbers large enough to:

• overwhelm defensive systems,
• force adversaries to reveal hidden sensors,
• exhaust their ammunition,
• create multi-vector pressure in chokepoints,
• and probe denied areas without risking a crewed ship.

The same logic that allowed Ukrainian USVs or Houthi maritime drones to challenge modern navies now applies underwater — but with the added difficulty of the ocean’s opacity.

Characteristics of attritable underwater systems

• Rustic and robust: few moving parts, tolerant to shock and pressure.
• Inexpensive: built from COTS components, 3D-printed structures, or non-metallic hulls.
• Minimal logistics: deployable from RHIBs, land vehicles, or even aircraft.
• Expendable: designed to be lost, jammed, or sacrificed during missions.
• Mass-scalable: suitable for swarming concepts or pre-positioned “smart mines”.

6. Startups landscape

The structural shift toward distributed, autonomous, and data-driven systems below the surface has created a fertile ground for high-growth, technology-focused startups and scale-ups. The incumbent defense Primes are increasingly reliant on this dynamic ecosystem to rapidly integrate new capabilities that bypass legacy procurement cycles. Innovation is no longer centered solely on the large, exquisite, manned platforms of the past, but on the proliferation of attritable robotics , Edge AI for real-time sensing, and high-endurance power systems.

The companies listed below are driving this revolution, often focusing on a single, critical layer of the operational stack, from advanced Synthetic Aperture Sonar (SAS) and GPS-denied navigation, to AI-native signal processing and affordable, mass-producible UUV platforms. These specialists are essential partners for navies and system integrators seeking to transition from periodic monitoring to persistent underwater domain awareness.

7. Conclusion

The contest for underwater dominance is no longer a slow, technical competition fought in the shadows. It has become a strategic race, fast, disruptive, asymmetric, driven by the multiplication of autonomous systems, the fragility of seabed infrastructure, and the proliferation of cheap, rustic underwater drones capable of mass and saturation. What once required a nuclear submarine, or a specialized minehunter, can now be attempted with a handful of low-cost platforms and commercially available components.

This transition forces states and navies to rethink everything, from how they sense and patrol, to how they protect, deter, and respond. The old model, built on a few exquisite platforms and episodic awareness, cannot keep pace with adversaries who leverage autonomy, attritability, and scale. The future belongs to distributed systems: networks of AUVs, USVs, resident nodes, edge-AI processors, seabed sensors, and autonomous logistics chains operating as a coherent system of systems.

The stakes extend far beyond military advantage. The seabed has become a critical artery of global connectivity and energy resilience. A handful of simultaneous attacks on submarine cables or power interconnectors could destabilize entire regions. Protecting these assets is now a core element of national sovereignty. At the same time, underwater SAR, support and logistics, once niche functions, are becoming strategic enablers of operational tempo and crisis response.

The revolution described in this report is underway but not yet won. The technology exists; what is missing is scale, integration, and speed of adoption. No navy, or nation, can succeed alone. The next decade will reward those who embrace collaboration between defense primes, startups, software companies, and deep-tech innovators, and who build open architectures rather than closed stovepipes.

The underwater domain is becoming the next strategic frontier. The question is no longer whether this revolution will reshape defense, but who will shape it.

Call to Action

To remain credible and protected in this new era, nations and industry leaders must act now:

• Invest in scalable autonomy, not incremental upgrades
• Accelerate system-of-systems integration across USVs, AUVs, seabed nodes and C2
• Adopt open architectures that allow rapid insertion of new payloads, AI models,
  and autonomy stacks
• Mobilize startups and scale-ups as core innovation partners, not peripheral suppliers
• Build a sovereign industrial base capable of producing low-cost, attritable underwater systems at scale
• Develop doctrine and capabilities for counter-UUV and swarm defense, urgently

The nations that move first will shape the rules, build deterrence, and secure the deep ocean for decades. Those who wait risk fighting tomorrow’s war with yesterday’s tools.

The next strategic revolution is happening underwater.

It is already here.

The only choice left is whether to lead it, or be forced to adapt to it.