Submarines have long played a crucial role in naval strategy, offering nations a stealthy and powerful way to project force and monitor threats beneath the surface. But the tide is turning. Instead of relying solely on costly, crewed vessels, militaries are now deploying fleets of autonomous underwater vehicles (AUVs) to protect critical infrastructure and expand surveillance in deep, hard-to-reach waters. At the forefront of this shift is European defense startup Helsing, whose new AI-powered mini-submarine, the SG-1 Fathom, is making waves.
Small but mighty, the SG-1 Fathom is just under two metres long, weighs only 60 kilograms, and is built for speed, silence, and smarts. Its hydrodynamic frame is inspired by underwater gliders, and instead of traditional propellers, it uses a buoyancy engine to move – quietly and efficiently. What powers its intelligence, though, is “Lura,” a large acoustic model trained on decades of underwater sound data. Think of it like a large language model, but instead of understanding text, it interprets the unique acoustic fingerprints of vessels in real time.
Lura gives the SG-1 a critical edge. Its four passive sonar sensors can detect sounds ten times quieter and process them forty times faster than a human operator. Because it relies on passive sonar rather than active signals, it stays hidden while it listens, making it ideal for stealth operations. The mini-sub can classify and geolocate other submarines, ships, or drones without revealing its own presence.
This new class of underwater AI agents isn’t just smart—they’re scalable. Hundreds of SG-1 Fathoms can be launched simultaneously, forming a silent constellation under the sea. Each sub operates independently, only surfacing briefly to send encrypted updates to satellites. A single operator can monitor the entire swarm from a command centre, getting near real-time insights without deploying a crewed mission. The potential for persistent, low-cost surveillance of vast maritime zones is game-changing—especially when it comes to protecting undersea internet cables and deterring hostile submarine incursions.
Helsing’s Rapid Rise and Strategic Edge
Founded in 2021, Helsing has quickly become one of Europe’s most important defense tech startups. Backed by big names like General Catalyst and Saab, the company raised €209 million in Series B funding in 2023, followed by an even larger €450 million round in mid-2024. That funding boost pushed Helsing’s valuation to nearly €5 billion and cemented its position as a key player in the future of European defense.
But Helsing isn’t just innovating underwater. Its AI is being built into jets like the Saab Gripen and integrated into next-generation combat systems through deals with Airbus and Rheinmetall. The company has also teamed up with Mistral AI to build “vision-language-action” models, aiming to improve battlefield decision-making by helping machines understand complex real-world scenarios. One major project in the works is the Wingman, an unmanned fighter drone developed with Airbus to fly alongside human-piloted jets.
This cross-domain strategy shows that Helsing isn’t limiting itself to the sea. Instead, it’s laying the groundwork for a defense ecosystem where AI plays a central role—on land, in the air, and underwater.
The SG-1 Fathom’s launch comes at a time when undersea infrastructure has never been more at risk. The 2022 Nord Stream pipeline sabotage served as a wake-up call. Since then, protecting Europe’s underwater assets has become a priority. With the EU’s €800 billion “ReArm Europe” initiative aiming to modernise military readiness, AI-powered submarines like SG-1 are poised to become a key part of that future arsenal.
Globally, Helsing faces stiff competition from U.S. defense startups like Anduril, Shield AI, and Skydio. Anduril, for instance, is building the Orca XLUUV for the U.S. Navy—a much larger, long-range autonomous submarine. Shield AI recently raised $240 million, bringing its valuation to $5.3 billion, signalling just how competitive the race has become to lead in defense autonomy.
Still, Helsing’s advantage lies in its ability to move fast, iterate continuously, and adapt across multiple military domains. As Amelia Gould, General Manager of Helsing Maritime, put it, the SG-1 Fathom and Lura form a defense cycle that learns with every mission—allowing Europe to outpace emerging threats with real-time intelligence and rapid deployment.
Co-CEO Dr Gundbert Scherf summed it up: “Lura detects so our navies can deter. We must harness new technologies to keep pace with the threats against our critical infrastructure, national waters, and way of life.”
