There is a certain clarity to the problem Tethys Robotics is trying to solve. You cannot see. The water is thick with sediment. The current wants to push your expensive equipment into a turbine foundation or a bridge pylon. This is the reality of inspecting critical underwater infrastructure, a task still reliant on human divers or remotely operated vehicles (ROVs) tethered to surface vessels. The cost is measured in hundreds of thousands of euros, vessel emissions, and human risk. The solution, according to the seven founders who spun out of ETH Zurich in 2024, is a 35-kilogram robot that does not mind the dark.
Tethys Robotics AG is building the Tethys ONE, a hybrid ROV/AUV (autonomous underwater vehicle) designed for what the industry politely calls "challenging environments." Turbid, high-current waters around offshore wind farms, hydropower dams, and port infrastructure are precisely where conventional optics fail. Tethys ONE leans on sensor fusion,combining sonar, ultrasonic, and visual data,to navigate and map structures when cameras see only soup [Venturelab]. The claim is a robot that can be deployed in ten minutes, operate for four hours on a single charge, and reach depths of 300 meters [36Kr]. For operators, the math is simple: less vessel time, lower cost, fewer carbon dioxide emissions, and no divers in harm's way.
The wedge in murky water
The company's bet is not on building a better robot for clear, calm seas. That market has established players like Saab Seaeye and Blueye Robotics. The wedge is precision in chaos. Offshore wind farms, a core target, are being built farther out and in deeper, rougher waters. Annual inspections of foundations and cables are mandatory and notoriously expensive. A robot that can perform these inspections autonomously in zero visibility represents a direct attack on the operational budget line that hurts most.
- Technical pedigree. The founding team cut its teeth building competition-grade underwater vehicles as ETH students, winning the Gwyn Griffiths Underwater Robotics Award in 2024 [Wyss Zurich]. This is not a software team learning hardware; it's a hardware team applying academic rigor to an industrial problem.
- Market timing. Europe's push for energy independence has accelerated offshore wind deployment. The global subsea inspection market for renewables and infrastructure is estimated at over €5 billion [Venturelab]. Regulatory pressure for safer, greener operations adds tailwinds.
- The hybrid model. By operating as both a tethered ROV and an autonomous AUV, Tethys ONE aims to cover the full inspection workflow,from close-up, pilot-controlled detail work to pre-programmed, wide-area surveys.
From the lab to the limfjord
Traction for a deep-tech hardware startup is measured in pilots and partnerships, not monthly active users. Tethys reports over 30 pilot projects are underway, including collaborations with the Swiss Army and the Swiss Disaster Relief Corps for ordnance disposal and search missions [Robert Katzschmann LinkedIn]. A partnership with offshore service specialist SeaRenergy aims to validate the technology in the field for wind farm operators [Offshore Technology]. These are the necessary, gritty steps to prove reliability to a conservative customer base.
The company has grown to a team of 18 since its 2024 founding and has been named to the TOP100 Swiss Startups list for 2025 [36Kr]. Funding has followed a classic European deep-tech path: grants and non-equity assistance from entities like Venture Kick and Wyss Zurich, followed by an undisclosed pre-seed round in 2025 from investors including Redstone and Alpine VC [Venturelab, StartupTicker]. The runway appears to be extending toward a seed round targeted for late 2025 [Wyss Zurich].
The dive profile gets steeper
The path from successful pilot to recurring enterprise contract is a steep climb, especially underwater. The risks are not subtle.
The hardware gauntlet. Saltwater, pressure, and debris are merciless. Proving a 99% operational uptime over hundreds of dives in varied conditions is a multi-year engineering slog that grant money alone cannot buy.
Sales cycles in a hard hat industry. Offshore wind operators and large utilities move slowly. Purchasing a novel robotic system involves stringent health, safety, and environmental (HSE) reviews and capital expenditure committees. A long proof-of-concept phase is almost guaranteed.
The incumbent response. Companies like Saab Seaeye have decades of domain knowledge and customer relationships. Their systems are the known quantity. Tethys must prove not just technical superiority in niche conditions, but also that its business model,potentially robotics-as-a-service,can undercut the total cost of ownership of established, vessel-heavy methods.
Tethys's answer lies in its specificity. It is not selling a general-purpose underwater drone. It is selling a solution for the specific, expensive, and growing problem of inspecting assets in poor visibility. Every pilot with a wind farm developer is a chance to build the case study that unlocks the next ten contracts.
The unit economics of clear water
Let's put a rough number to the ambition. A traditional inspection of a single offshore wind turbine foundation using a crewed vessel and an ROV can cost between €50,000 and €100,000 per day, with operations often spanning multiple days. The vessel itself is a major source of cost and emissions.
If Tethys ONE can be deployed from a smaller, cheaper vessel,or eventually from the turbine platform itself,and complete a foundation survey in a single four-hour dive, the potential savings are substantial. Slash the vessel time by 75%, and you are looking at a cost per inspection that could be under €25,000. For a wind farm with 100 turbines, the annual inspection bill could drop from millions to a number that makes finance directors take notice. The carbon dioxide savings from reduced vessel fuel would be a meaningful side effect, measured in tens of tons per campaign.
The company Tethys must beat is not a startup. It is the entrenched operational habit of sending a ship and a team out into the North Sea. Its robot is not just a piece of technology, it is a argument for a different, quieter, and cheaper way of keeping the lights on.
Sources
- [Venturelab, 2025] Tethys Robotics AG - Venturelab | https://www.venturelab.swiss/tethys-robotics
- [36Kr, 2025] Swiss Robotics Firm Tethys Robotics Develops Underwater Inspection Robots | https://eu.36kr.com/en/p/3529775629981833
- [Wyss Zurich, 2024] Tethys Robotics AG brings smart underwater drones to the deep - Wyss Zurich | https://www.wysszurich.ch/news/tethys-robotics-ag-revolutionizes-underwater-mapping-with-smart-autonomous-drones
- [Robert Katzschmann LinkedIn, 2026] Post on Tethys Robotics collaborations | https://www.linkedin.com/company/tethys-robotics/
- [Offshore Technology, 2026] Tethys Robotics partners with SeaRenergy | https://www.offshore-technology.com
- [StartupTicker, 2026] ETH-Spin-off secures €3.5 million to advance its under water robot | https://www.startupticker.ch/en/news/eth-spin-off-secures-3-5-million