Beneath the Waves

Junaid Suhais

In 1945, when Oppenheimer’s creation flattened Hiroshima and Nagasaki, the world assumed the future of war would be written by nuclear fire. For decades, strategy and deterrence revolved around warheads and delivery systems. But if the past two years in Ukraine have shown anything, it’s that the decisive weapons of this century may not be nuclear at all. Cheap drones, once dismissed as hobbyist gadgets, are rewriting battlefields, swarming tanks, ambushing artillery, and neutralising air defences. Traditional hardware, such as heavy armour and manned aircraft, suddenly appears exposed.

The lesson is simple: technology is bending warfare toward autonomy, persistence, and mass deployability. And while the skies of Ukraine have made this evident, a new frontier is silently opening under the surface. The nations of the world are racing to build autonomous underwater vehicles: drones of the deep, that will change the way navies fight, spy, and survive at sea.

Unmanned Underwater Vehicles

Unmanned underwater vehicles (UUVs), also abbreviated as undersea drones, are robot systems that submerge and operate without a human crew. UUVs can be divided into two basic types: Remotely Operated Vehicles (ROVs), which are controlled by a human operator with a tether, and Autonomous Underwater Vehicles (AUVs), semi-autonomous or autonomous systems that operate with preplanning (i.e., it’s programmed) or autonomous sensor-driven missions. UUV technology has transitioned rapidly over the last couple of years from an academic novelty to an essential military capability, and some can counter offensive actions as an independent, robotic system or target enemy vessels.

Undersea drones are rapidly changing the nature of naval warfare with decreased human exposure while making high-risk decisions. UUVs’ defensive applications can include mine countermeasures, surveillance, and protection of critical infrastructure, while the offensive application may include mission planning and intelligence gathering behind enemy lines. UUVs are also employed in combat operations.

Defensive Missions

One of the earliest and most significant uses of UUVs in defence is mine countermeasures (MCM). Navies deploy AUVs to search for and neutralise naval mines in harbours and shipping lanes. For example, the US Navy’s Knifefish AUV is designed to autonomously hunt mines, allowing for safe route clearance during fleet operations.

The United Kingdom (UK) has also received REMUS-series UUVs capable of improving its mine hunting capability. The Russo-Ukrainian War emphasised the devices used for MCM: as the number of sea mines increased in the Black Sea, Western navies stepped up efforts to get UUVs for mine-clearing out to operate and ensure freedom of navigation. For example, the UK Royal Navy acquired the support ship RFA Stirling Castle in 2023 to support a fleet of unmanned minehunters and AUVs to counter the renewed mine threat.

The UK has also procured REMUS-series UUVs to increase the availability of mine hunting capability. The Russo-Ukrainian War has increased the value of MCM, as sea mines are deployed in the Black Sea, Western navies have accelerated their pace of fielding UUVs for mine-clearing to allow for unimpeded freedom of navigation. An example is the Royal Navy acquiring the support ship RFA Stirling Castle in 2023 to deploy a cadre of UUVs and AUVs to respond to the now renewed mine threat.

In addition to mine hunting and mine neutralisation, UUVs can also provide significant value more broadly in the role of Intelligence, Surveillance, and Reconnaissance (ISR) capabilities, which can enhance security-wide maritime domain awareness. UUVs can collect intelligence by covertly monitoring enemy coastal waters, monitoring submarine movements, tracking vessels, and mapping the ocean environment. AUVs can augment the fight against anti-submarine warfare (ASW) and establish undersea sensor barriers.

Finally, for surveillance of critical undersea infrastructure itself—such as communications cables and pipelines—UUVs can conduct inspection and monitor illicit incursions. UUVs process technologies that took time to develop fully, meaning that some of the capabilities may not be fully utilised initially; however, UUVs present an undeniable capability that found relevance in the wake of the attempted sabotage of the Nord Stream natural gas pipelines in September 2022. The act of sabotage and its implications also drew attention to the threats to undersea assets while cementing the requirement for vigilance.

Offensive Missions

While historically used in support roles, undersea drones are increasingly being considered for offensive operations—delivering kinetic effects and projecting power underwater. A major offensive use is clandestine minelaying. The US Navy’s Extra-Large UUV programme, known as Orca, is explicitly developing a long-range autonomous submarine drone to lay mines in enemy waters without exposing a manned submarine.

The first Orca prototype began sea trials in 2023, and the navy is evaluating how such UUVs can expand its offensive mine warfare capabilities. More controversially, Russia and North Korea have each claimed to test nuclear-armed autonomous torpedoes—Russia’s Poseidon and North Korea’s Haeil-2—which blur the line between UUV and strategic weapon. While these systems are extremely large and nuclear tipped (and thus not typical UUVs), they represent a push toward offensive undersea drones with strategic impact.

Another emerging offensive role is as a hunter-killer or strike platform. The US Defence Innovation Unit (DIU) in 2025 issued a call for ‘one-way attack’ UUVs—essentially underwater kamikaze drones—that could be launched from submarines to seek out and destroy enemy ships or submarines. An extra-large UUV can carry jamming equipment or deploy sensors deep behind enemy lines.

Global Overview

US Navy

The US Navy has a wide variety of USVs and has a modular, multi-mission focus.

XLUUV-Orca (Boeing): Diesel-electric hybrid, range 6000 nm, 10 m payload bay (payload of 8 tons). Missions including mine laying, ASW, ISR. Prototype on initial trials at sea (2023) and up to five units remain to be ordered.

LDUUV-Echo Voyager: 50 tons; 15 m; 3000 nm stem specifications (tested 2017-2019). Design specifications of Orca derived from Echo Voyager characteristics.

Heavyweight UUVs: Knifefish (mine hunting), Bluefin-21 (surveillance). Endurance in the tens of hours.

Justification: Undersea dominance, expansion of operational reach through unmanned systems and also manned-unmanned teaming & distributed fleet concept.

Russia

Nuclear Deterrent and Arctic Missions

Poseidon: 20 m nuclear power/nuclear-armed torpedo. Strike capability intended against strategic coastal targets. Depth claimed to profess depth of 1000 meters and speeds greater than 50 knots. Testing ongoing. 

Sarma (Lazurit): XLUUV for Arctic under-ice missions. Claimed 8,000km of range, months-long endurance through air-independent propulsion.

Other systems: Smaller UUVs for seabed operations, special missions. Historical focus on cable tapping, deep-diving submersibles (e.g., AS-12 Losharik). Concepts of torpedo-armed UUVs displayed at expos.

Rationale: Offset NATO naval advantage, ensure second-strike deterrence, dominate Arctic sea lanes, cheaper modernization path for the navy.

China

Expansion and Export

Sea Wing glider: Oceanographic/intelligence tool. Dozens are deployed in the South China Sea and the Indian Ocean. Supports military oceanography and ‘underwater Great Wall’ surveillance network.

UUV-300 (export): 12 m, about 50 tons, 300 m depth, about 450 nm range at 5 knots. Two torpedo tubes + mine payload. Shown in 2024 (Malaysia). Among the first exported armed UUVs.

Domestic XLUUVs: Satellite imagery (2023) revealed PLAN prototypes about 11–12 m long. Weaponised designs with torpedo/ mine capacity.

Novel concepts: Amphibious ‘Feiyi’ drone (unveiled 2023)—swims then flies, reconnaissance/ strike potential.

Rationale: Enforce maritime claims, expand A2/AD network, complicate U.S./allied operations, gain influence through exports, match U.S. undersea edge. Over 150 UUV projects are active in Chinese institutions.

India’s Undersea Uncrewed Systems

India operates in a challenging maritime theatre comprising a large coastline, strategic island territories, as well as maritime threats from both the Indian Ocean and the continental aspects. The navy approaches unmanned systems, including undersea uncrewed systems, as significant contributors to regional security and safety on India’s maritime front. The current bureaucracy builds upon indigenous capabilities and focuses on coastal security, limited surveillance, and ultimately deep ocean reconnaissance and offensive capabilities.

Current Capabilities: India’s UUV capabilities remain limited compared to the US or China but are progressing. The navy has experience with ROVs for ship inspections, salvage, and debris clearance. These tethered systems, while not autonomous, form part of India’s underwater robotics base.

On the autonomous side, prototypes are still underway. The most recent was Neerakshi, a lightweight unmanned underwater vehicle (UUV) that is intended for mine detection, neutralisation, and underwater surveys and was created by Garden Reach Shipbuilders & Engineers (GRSE) in July 2023. At around two metres in length, the AUV can either be deployed from ships or coastal stations to secure harbours and shipping channels, while divers are at less risk.

The Defence Research and Development Organisation (DRDO) is developing a High Endurance AUV (HEAUV) at the Naval Science and Technological Laboratory. Intended for 24–48 hours of operation in deeper waters, it is seen as a precursor to long-range UUVs.

India is expanding its unmanned undersea programs with a mix of gliders, AUVs, and larger long-endurance systems. In 2021, former navy chief Admiral Karambir Singh mentioned ‘underwater domain awareness’ as a critical area, mentioning the Chinese autonomous underwater gliders found lurking in Indonesian waters in 2020.

Not long after, in October 2021, Vice Admiral Ashok Kumar, who was then vice chief of the navy and is now the first national maritime security coordinator (NMSC), released a comprehensive roadmap of the navy’s requirements for unmanned platforms, which he voluntarily shared with the domestic industry.

As a major milestone, in April 2023, the ministry of defence (MoD) announced to the world its plans to develop an Extra-Large UUV (XLUUV) in-house. The navy announced interest in acquiring, as appropriate, up to 12 units once a prototype proved successful. The proposed platform, potentially over 50 tons with endurance measured in weeks, is envisioned for deep-ocean surveillance, anti-submarine warfare, and mine warfare. Classified as a Make-I project, it will be government-funded with industry participation, reflecting India’s intent to develop this capability domestically.

Since the start of the India-US Defence Technology and Trade Initiative, there have been technical exchanges in the area of unmanned systems, and in 2021, India participated in the US-led Unmanned Systems Integrated Battle Problem exercise, which integrated undersea drones. Indian defence companies have partnered and imported various sophisticated components like sonar from Israel and inertial navigation systems from Western companies for use in prototypes but have so far emphasised greater self-reliance in undersea warfare under the Aatmanirbhar Bharat framework, using domestic sources for design and manufacture of UUVs rather than relying on imports.

Integration into Maritime Strategy and Doctrine: India’s maritime strategy documents increasingly highlight unmanned systems as central to securing the Indian Ocean Region (IOR). The Indian Navy’s Concept of Operations for Unmanned Systems (2021) and Unmanned Systems Roadmap (2021–2030) emphasise UUVs for surveillance, particularly in response to China’s growing undersea presence.

Extended Surveillance and Domain Awareness: UUVs extend India’s reach across the IOR, monitoring choke points like Malacca, the Andaman Sea, and the Persian Gulf approaches. They compensate for limited submarine numbers by acting as persistent ‘tripwires’ against intrusions. Long endurance AUVs and XLUUVs can loiter for days, collecting intelligence while keeping crews safe. Nearly 80 per cent of India’s external trade and 90 per cent of its energy imports travel through these oceanic routes.

Coastal Security and Mine Countermeasures: UUVs enhance coastal defence by searching for mines, divers, or sabotage near critical ports and harbours where critical infrastructure lies. The Neerakshi AUV is designed for shallow water, and can identify and neutralise threats to ports, and aims at learning lessons from the heinous 2008 Mumbai attack. Using UUVs as part of a mine-countermeasure flotilla guarantees no danger to the operator while opening sea lanes or accessing ports during combat.

Deterrence and Offensive Options: While framed as defensive, Indian UUVs are envisioned for mine-laying and anti-submarine roles. They could interdict enemy submarines or seal waters with mines, projecting power at lower risk. The rise of armed UUVs in China and Pakistan makes such capability a necessary deterrent.

Countering China’s Influence: China’s seabed mapping, Djibouti base, and submarine patrols highlight its undersea push. India is responding with gliders, AUVs, and XLUUV projects positioned near key chokepoints. Quad partnerships, including undersea domain awareness initiatives, enhance India’s ability to track and counter Chinese submarines.

Other Key Nations

United Kingdom: The Royal Navy uses REMUS 100/300 AUVs and the Saab Seaeye Falcon ROV. In 2022, it launched Project Cetus, a 12 m, 17-ton Extra-Large UUV built by MSubs, aimed at testing long-endurance autonomous ops and future tech. The UK seeks to extend submarine reach and protect undersea cables, also collaborating with the US via AUKUS Pillar II. In 2025, British subs ran a trial of torpedo-tube launch and recovery of UUVs.

France: The French Navy, with experience in systems like the Victor 6000 ROV, is now developing autonomous platforms. Naval Group is building a 10-ton, 10 m UCUV demonstrator under a 2023 DGA contract, targeting late-2020s trials. Focus areas include EEZ patrols, nuclear sub support, and coalition operations such as REPMUS.

Germany: Germany has long used REMUS 100 AUVs and participates in NATO MMCM-US programs. TKMS is developing the MUM (Modular Underwater Mothership) as a large UUV concept. Strategic priorities remain mine countermeasures and Baltic/ North Sea security.

Japan: Developed the Urashima AUV (317 km endurance, 2005); exploring military coastal monitoring.

South Korea: Tested mine-hunting UUVs, working on larger AUVs against North Korean subs.

North Korea: North Korea unveiled the ‘Haeil,’ its first-ever nuclear-armed unmanned underwater vehicle (UUV)in 2023.

Israel: Israel has displayed armed UUV concepts.

Turkiye: Turkiye’s leading defence company, Aselsan, unveiled the UUV ‘Deringöz at the IDEF 2023 defence fair in Istanbul in July 2023.

Australia: Australia is also working on a prototype uncrewed underwater vehicle named Ghost Shark

Analysis

Undersea drones mark a sea change in naval warfare, providing many advantages in range, persistence, and risk to humans, while also introducing significant risk if not executed wisely. As technology matures, we can expect naval forces globally to pivot their strategies and doctrines to include Uncrewed Undersea Vehicles (UUVs) as a key part of any naval force structure. For the nation-states that can use the benefits of undersea drones while mitigating risk, they will have a clear advantage in the maritime security realm in the 21st century. For India, this means continuing to invest in domestic UUV capabilities and contributing to multinational endeavours to create the rules of the road for these new tools. The undersea domain is no longer the domain of manned submarines; it represents a contested space in which unmanned applications, friend and foe, will have an increasing role in informing