At 12:26 on Christmas Day 2024, the Estlink 2 power cable between Finland and Estonia went dark, dropping cross-border capacity from 1,016 megawatts to 358. By the time Finnish authorities had pieced together what happened, a 74,000-deadweight-tonne crude oil carrier called the Eagle S, sailing under a Cook Islands flag of convenience, had dragged its anchor along the Baltic seabed for almost 100 kilometres, tearing through the power line and four telecommunications cables as it went. The Finnish Coast Guard boarded the tanker the following day. Within weeks, NATO Secretary General Mark Rutte announced the alliance would launch a dedicated operation, Baltic Sentry, to put frigates, maritime patrol aircraft and naval drones above a stretch of water that Europe had spent decades assuming was safe.
Baltic Sentry began on 14 January 2025. Rutte's justification turned on a set of numbers that had become impossible to ignore. More than 1.3 million kilometres of submarine cables carry over 95 per cent of global internet traffic and move roughly $10 trillion of daily international trade. The physical infrastructure holding the internet together sits on mud and sand, often in shallow water, in many cases unmonitored. Nord Stream in September 2022 was the first signal that somebody had noticed. Estlink 2 made clear the signal was not going to stop.
The interesting consequence of that realisation is industrial, not political. Ten years ago, autonomous underwater vehicles with week-long endurance, torpedo-tube-launched surface drones and wireless magneto-inductive comms under water were the exclusive territory of a handful of primes. Today the companies building them mostly have fewer than 200 people and many were founded after 2020. Among the 45 naval and maritime companies we track across 15 European countries, the startup layer is where the non-trivial engineering is happening. For engineers who want to work on the hardest problems in underwater robotics, a 30-year career inside a large prime is no longer the only route in.
Eyes and ears on the seabed
Protecting a cable you cannot see starts with being able to see it. Underwater visibility is a harder problem than airspace or surface surveillance by every meaningful measure. Sound propagates unevenly through stratified water columns, optical sensors are blinded within metres in turbid conditions, and radio barely works at all below the surface. The companies we track in the sensing layer are the ones trying to fix that.
Havguard is a Norwegian startup founded in Leknes in 2023 and built on fourteen years of academic research into magneto-inductive underwater wireless communications. The company is developing multimodal acoustic, magneto-inductive and optical modems aimed at submarine detection and critical underwater infrastructure monitoring. EvoLogics in Berlin, founded in 2000 and with between 51 and 200 employees, has built a business around biomimicry. Its underwater robots borrow from penguin locomotion and its acoustic modems from the way dolphins communicate through water, both of which turn out to be better models than anything a human engineer would design from scratch.
ELAC SONAR in Kiel is the longest thread in the story. Founded in 1926, the firm has been working on hydroacoustic engineering for 100 years and still fits into the same size bracket as the newer startups around it. Nearby, north.io builds cloud platforms that turn raw sensor output from underwater instruments into something a navy analyst can actually use. Above the water, Unseenlabs in Rennes operates a small satellite constellation that picks up radio-frequency emissions from vessels at sea, including ships that have switched off their AIS transponders. Eagle S was the kind of "dark ship" Unseenlabs exists to detect.
Further south, SOTIRIA Technology in Athens is building the kind of passive sensing hardware that rarely makes the news but matters enormously in shallow coastal waters. Founded in 2021, the company sells a fluxgate magnetic sensor with pico-tesla sensitivity and a passive hydrophone covering 1 Hz to 100 kHz, and it packages both into a product called Nereid, an AI-powered underwater ISR system aimed at detecting stealthy submarines, divers and uncrewed underwater vehicles. SOTIRIA deployed its sensor network at a NATO exercise in 2023 and has since attracted interest from multiple allied navies. The significance of SOTIRIA is less about the company itself than about the fact that a 2021 Greek startup is now selling this class of capability at all, in a business that required a defence prime behind you as recently as the mid-2010s.
The vehicle layer
Sensors only matter if something can carry them. The autonomous platforms under development across Europe are where the capability gap with the Russian shadow fleet is closing fastest.
EUROATLAS in Hamburg is building the Greyshark AUV in two variants. The Bravo version runs on batteries. The Foxtrot version uses a hydrogen fuel cell and has a claimed endurance of up to 16 weeks or more than 10,000 nautical miles. Seventeen onboard sensors give it a mission set that spans ISR, anti-submarine warfare, mine countermeasures and critical underwater infrastructure protection. In August 2025 Rheinmetall announced a partnership to integrate Greyshark into its Battlesuite coastal defence framework. An AUV with months of endurance plugged into the battle-management software of a German prime is a non-trivial coupling, and it suggests the large players have accepted that the interesting designs are coming from smaller companies.
Exail in Paris is the counter-example. With between 1,001 and 5,000 employees it is closer to prime territory, and the work it does on the A18-M AUV reflects that scale. In November 2024 the French defence procurement agency DGA selected a Thales and Exail partnership for eight A18-M vehicles plus an option for eight more, integrating the SAMDIS 600 synthetic aperture sonar, for the French Navy's SLAMF mine-countermeasures programme. SLAMF is the kind of long-duration, structured naval acquisition that only primes can handle well, and France's mix of startup-scale and prime-scale players reflects that.
Kraken Technology Group in Fareham, Hampshire, has raised backing from the NATO Innovation Fund, the UK National Security Strategic Investment Fund and Superangel. Its K4 Manta is a hybrid surface-subsurface platform built around a carbon foiling structure, able to fly on the water and then submerge. The company has a US SOCOM Other Transaction Authority contract worth up to $49 million and sits on the Royal Navy's Project Beehive programme for 20 uncrewed surface vessels. Maritime Robotics in Trondheim, founded in 2005, is further along the commercial curve. Its Mariner USV has been available since 2016 and in 2019 it completed a single voyage of more than 7,750 nautical miles, a useful reality check on what autonomous surface platforms can already do without a crew.
Further east, the combination of Gabler Maschinenbau in Lübeck and FLANQ in Rostock is producing something that did not exist five years ago: a submarine torpedo-tube-launched surface drone. The Ranger and Raider share a 4.5 metre hull rated to 300 metres depth, with a folding mast and keel and an electric drivetrain. Ranger is reusable and tuned for ISR, while Raider is single-use and tuned for strike missions with a user-supplied payload. Gabler handles system integration and final delivery, FLANQ handles design and payload integration. A full-scale prototype is under assembly with initial sea trials scheduled for mid-2026, opening a submarine-launched USV capability that Europe has not previously fielded in its own yards.
The Polish cluster and the unusual bets
The geographic pattern in this sector is striking once you look at it. Norway and Germany lead on sensing and submarine technology, built on decades of Arctic and North Sea exposure and a deep acoustics heritage. Poland, Estonia, Latvia and Finland lead on the autonomous vehicle layer, with shorter histories but direct frontline exposure to the Russian shadow fleet. France sits in the middle with its large primes, and the UK brings composite hulls and hybrid surface-subsurface platforms that no other country is pursuing at scale. None of this is official policy. It matches where the engineering talent sits and where the threat is most acutely felt.
Poland is the specific surprise. We track seven Polish companies with a naval or maritime focus, more than any country except Germany, and almost nobody outside the industry talks about Polish defence beyond tanks. SR Robotics in Katowice raised €8.4 million in July 2025 from the Vinci Fund managed by the BGK Group, earmarked for production scale-up and a Robot-as-a-Service fleet targeting unexploded ordnance detection and critical underwater infrastructure protection. Blue Armada Robotics in Gdansk, founded in 2021 with between 11 and 50 employees, is the only Polish company in NATO DIANA's 2025 marine security cohort, developing hybrid-electric vessels capable of two-week autonomous missions. Enamor in Gdynia, a Gdynia Maritime University spin-off with NATO SECRET clearance, keeps 98 specialists working on navigation, communication and automation systems for the Polish Navy. Gdynia has been a serious maritime engineering town since the 1920s, and the cluster is the Baltic Sea threat layered on top of that inheritance.
The more unusual bets sit around the edges. SEATOM Technologies in Porvoo, Finland, is developing micro-nuclear reactor systems for marine and seabed operations under a programme called OCEAN-SMR, and it has been selected for NATO DIANA's Operations in Extreme Environments cohort. A startup building small nuclear reactors for AUV and seabed power is the kind of thing that either fails completely or changes the economics of long-endurance undersea operations. SUBmerge Baltic in Riga, founded in 2022, took its PIKE AUV to DSEI 2025 with a 150 kilometre range, a 500 metre depth rating and a 20 kilogram payload. Stickleback Robotics in Tallinn, founded in 2025 and with fewer than ten people, is already talking about its Morpheus and Neo platforms carrying 180 kilogram payloads in sea state 4 conditions with swarm coordination. Baltic Workboats on the Estonian island of Saaremaa has delivered more than 200 patrol vessels to over 20 countries and now integrates remote weapon stations on its Navy 45 WP platform.
The full list, mapped by country and industry, sits on our company directory.
Three years ago, this sector moved at the pace of a shipyard. Today it moves at the pace of a seed-stage hardware startup with government customers waiting for prototypes to hit the water. For engineers who like acoustic comms in turbid environments, autonomy in zero-visibility conditions and long-endurance power for platforms that cannot surface, the opportunity set has never been wider or more interesting. The harder question sits on the operator side. European navies assumed the seabed was safe for most of the post-Cold War period, and the doctrine, procurement timelines and training pipelines built on that assumption are not yet ready to absorb what these companies are producing. Baltic Sentry is the start of the adjustment. Whether the navies can integrate AUVs, USVs, magneto-inductive comms and dark-ship satellite detection into a single operational picture fast enough to keep up with the cables being cut is the question the rest of the decade will answer.
Kyiv
Kyiv