Much of our civilization is built on underwater infrastructure. We get our energy from oil and gas platforms, hydropower plants, and offshore wind farms; we transport this energy through subsea pipelines. Even our digital world relies on data cables crossing ocean floors on this blue planet.

Yet the sea is a harsh place: underwater structures suffer corrosion, heavy currents, earthquakes, fishing accidents, and even sabotage. Regular, frequent inspections are necessary, and that means sending highly specialized workers for weeks on end on isolated boats and ocean platforms. These people must dive in rough and dangerous conditions or operate vessels manually through murky waters.

Some widespread underwater structures are less welcome: there are still 1.6 million tons of WWII ammunition on the bottom of the Baltic Sea. Even Swiss lakes contain 8,000 tons of unexploded munitions! Despite all these decades, it might only take a landslide or a new subsea infrastructure project to set off the residue. We just haven’t had the tools to thoroughly inspect the ground beneath our bodies of water.

These are some of the problems our portfolio company wants to solve by making underwater mapping easier, safer, and more affordable.

Clever fusion of navigation sensors and algorithms

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Jonas Wüst is the CEO and co-founder of Tethys Robotics, an ETH spin-off that builds underwater drones for automated inspection and assessments in rough waters. Tethys robots have many applications, but Jonas says offshore energy and maritime safety have gained the most interest among potential customers.

Operating underwater is brutal for humans and challenging for robots. Beyond the obvious hardware strain from salt and water pressure, underwater drones can’t use GPS for satellite navigation or camera systems for visual localization. The team at Tethys had to come up with alternative ways to localize the robot and map its environment. As a result, the fusion of different navigation sensors and “probably the most accurate localization algorithm in a small-scale underwater robot” – according to Jonas – are what makes the Tethys drone unique.

The Tethys device is not just another dumb vehicle you turn with a joystick. Sure, it can also function as a Remote Operated Vehicle (ROV) with exceptionally small dimensions and great mapping skills. But the Tethys drone can also just be dropped into the water with custom instructions, and the robot will act autonomously. In this mode, the operating human can focus on reviewing the real-time data feed instead of squinting at a camera display simply to get around.

Using a Tethys robot means not having to send a human diver into a dangerous situation. And because the drone is smart enough to work autonomously, their human operators don’t need as much training as typical ROV controllers. Tethys robots can be deployed from existing fleets and platforms, but in the future they can be combined with autonomous surface vessels to replace diesel-fueled boats and operated all the way from the shore. This means reducing risk to humans, saving the operating companies’ money, and cutting carbon emissions for everyone’s benefit.

Building a sea drone in a landlocked country

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It might seem surprising that a start-up from a landlocked country develops tools that are predominantly used at sea. Yet Switzerland is just as much a part of the blue planet as countries with stretching ocean shorelines: we are rich with deep lakes and turbulent rivers. Jonas explains that the founding team of Tethys Robotics includes a few enthusiastic divers, so underwater conditions aren’t alien to the developers.

Going into subsea robotics was also a business strategy. On the one hand, Switzerland is a global hotspot for robotics – “Silicon Valley of robotics”, Jonas describes. This means new founders have access to a lot of peer support and shared industry intelligence. On the other hand, the ecosystem had produced many great robots that operate on land and in the air, but hardly any underwater drones. Jonas and his team saw a niche for a blue ocean strategy.

Tethys Robotics started as a hobby project in 2018, as Jonas and his six co-founders were itching to balance their theory-heavy studies with something more hands-on. In just four months, the ETH engineering bachelor students designed and built a prototype that landed among the top 10 drones of the MATE ROV World Championships in the United States. This drew attention back home, and ETH Zurich encouraged the team to develop their technology further.

With their strong hardware focus, the Tethys team struggled at first to find a suitable space to build and test their systems. That first ETH garage they occupied might not have been entirely official, but it was a tech company classic. A real leap forward happened when the group got permission to use a nearby public swimming pool for testing during the small hours of the night. Eventually the prototype was robust enough to test in the natural waters of Lake Zurich, and the engineers could return to a more sustainable diurnal rhythm.

Preparing for first revenue and seed round

The size of the founding team was another challenge: the seven friends were all fully committed to the project, and finding early funding to feed seven developers is a feat. A combination of very lean years and fortunate parallel grants got the team through the early days; today Jonas is grateful for the financial runway enabled by Wyss Zurich, Venture Kick, Kickfund and a few other early supporters. Tethys Robotics now has 15 permanent employees, including the entire original founding team.

Tethys won the final Venture Kick stage in 2023 and joined the Kickfund portfolio in January 2025. The company launched their flagship robot, Tethys ONE, in 2024, and the first drones will be deployed later this year through both sales and subscription models. This is an exciting time for Jonas: getting to work with customers and finessing production processes is an important milestone in any deep-tech project. Jonas’s team also expects to close a seed round of a few million francs by the end of 2025.

Looking into the future, Tethys plans to become the leading company in subsea inspections in the next decade. The company continues to develop hardware, but Jonas is also looking forward to strengthening their software offering. The entire underwater inspection branch is going to become more digitized, Jonas explains. Tethys’s mapping competence will help them meet the growing need for solutions like 3D models and digital twins.

Popular culture gets fussy about robots. Our imagination paints pictures of human-like androids with artificial general intelligence; depending on our disposition, we see them either as capable saviors or ruthless terminators. Jonas would welcome more reality in the conversation: contemporary robots are already out there in the world, improving quality of life as well as corporate bottom lines. They do it without flashy futuristic esthetics or catchy existential crises; they are real tools, not fever dreams whipped up by screenwriters. Many of those tools come from Switzerland, and soon some of them will replace humans in dark and dangerous waters.

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‍Tethys Robotics is one of the rising companies mentioned in the Swiss Deep Tech Report 2025. Read more about the report here.