The water others
can't dive.
SepcoTech represents Tethys Robotics — an ETH Zurich spin-off from Switzerland — and its Tethys One: a rugged, tethered hybrid ROV/AUV — piloted and autonomous — built for the missions divers can't risk. Zero visibility, strong current, contaminated water, unknown hazards on the bottom. It navigates, searches, maps and recovers where a human can't safely go.
When the water is too dangerous for a diver.
Rivers, harbours and floodwater are the hardest environments to work in — near-zero visibility, strong current, debris and the constant risk of unexploded ordnance, lost evidence or a casualty on the bottom. Putting a diver in costs time, money and exposes a person to real danger. The Tethys One goes in instead: an autonomous drone that holds position in current, maps the seabed by sonar when the cameras see nothing, and brings back a clear picture — and the object — without a human ever entering the water.
One rugged drone, built for the worst water
The Tethys One is a compact 35 kg underwater drone two people can carry to the water's edge and have working in about ten minutes. Omnidirectional control — 360° in roll, pitch and yaw — lets it hold a stable inspection position even in a 3.5 knot current.
A Doppler velocity log and acoustic positioning let it navigate and run survey lines autonomously on its wired link, even with no GPS and no visibility. Forward-looking and multibeam sonar build interactive 3D maps of the bottom; HD cameras and lights confirm contacts; and an optional manipulator arm grabs and recovers objects — up to the weight of a fully-equipped diver.
See the full Tethys One platform →Key specifications
The headline figures a technical or procurement reader needs — full datasheet on request.
- Weight (in air)35 kg
- Operating depth300 m
- Tether (wired link)400 m, extendable
- Endurance4 h, hot-swap batteries
- Setup to in-water~10 min, two people
- Station-keepingHolds in 3.5 kn current
- MovementOmnidirectional 360° roll/pitch/yaw
- NavigationDVL + acoustic USBL positioning
- SonarForward-looking + multibeam 3D mapping
- CamerasFull-HD tiltable + stereo
- ManipulatorOptional 3-axis arm, ~2 kg lift
- Modular payloadsMetal detector, magnetometer, UT probe, sensors
Specifications per Tethys Robotics; configuration-dependent figures and payload options confirmed on enquiry.
Five missions, one autonomous platform
The same drone, configured and operated differently for each task — keeping personnel out of the water and shortening every search.
Humanitarian Demining
Survey lakes, rivers and shorelines for submerged mines and ordnance, map and identify each device by sonar, and support controlled removal — with divers kept clear of the blast radius.
Explore demining →
Infrastructure & Security
Inconspicuous, real-time inspection of harbours, hulls, quays, dams and critical underwater infrastructure — autonomous monitoring and threat search in turbid, high-current water.
Explore security →
Unexploded Ordnance
Locate and assess sunken munitions from past conflicts, build a 3D record of the site, and plan a safe, low-impact disposal — without sending a diver to an unknown device.
Explore UXO →
Police & Law Enforcement
Underwater search and recovery, evidence location and scene investigation — gathering real-time intelligence covertly and safely, before a police diver is ever committed to the water.
Explore police use →
Coast Guards
Underwater search-and-rescue, vessel and infrastructure inspection and threat monitoring across large patrol areas — extending reach in conditions that ground a dive team.
Explore coast guard use →Built with military EOD divers and armasuisse S&T
The Tethys One was developed together with the Swiss Command Explosive Ordnance Disposal & Demining and armasuisse Science & Technology — the Swiss government's defence-procurement science agency, through its Drone & Robotics Centre. The first prototype was delivered to the underwater EOD divers on 30 May 2022, against a backdrop of more than 8,000 tonnes of unexploded ordnance lying in Swiss waters.
It is the platform's defining reference — a system shaped alongside the divers who actually clear underwater ordnance, then carried across to the security, police and coast-guard missions below. The full EOD account, in the team's own words, is set out in the applications below.
Built for zero-visibility, high-current water
Four capabilities that let the Tethys One operate where a diver — or a camera-only ROV — simply can't.
Sees Without Light
Multibeam and forward-looking sonar build a 3D picture of the bottom when visibility is effectively nil — turbid harbours, silty rivers, floodwater.
Navigates Itself
DVL and acoustic positioning hold station and run survey lines autonomously, with no GPS fix and no surface reference.
Holds in Current
Omnidirectional thruster control keeps it steady for inspection work even in a 3.5 knot current.
Recovers Objects
An optional manipulator grabs and lifts — up to the weight of a fully-equipped diver — so it can bring evidence or ordnance to the surface.
No crane, no dive team, no vessel on station.
At 35 kg the Tethys One is carried to the water by two operators and ready in roughly ten minutes — from a quay, a RHIB or a riverbank. The mission starts where the threat is, not where a boat can reach.
The Tethys ONE drone system
Footage published by Tethys Robotics — the Tethys ONE autonomous underwater drone built for zero-visibility water.
A safe pair of hands for defence at sea
Authorised Distributor
We represent Tethys Robotics directly — specification, supply and through-life support, coordinated from one partner.
Naval & First-Responder Focus
A portfolio assembled for navies, coast guards, police and EOD units — not adapted from consumer kit.
One Point of Contact
Multi-supplier defence systems, integrated and quoted as a single package by one partner.
Backed Through Life
Training, spares and support for the full operational life of the system.
Speak directly with our defence specialist
Every enquiry is handled directly and in confidence — you will normally have a reply within one business day.
For spec sheets, capability documents, pricing or to arrange a briefing or demonstration — on this system or any platform in the SepcoTech defence portfolio — contact me directly:
- Spec sheets & technical datasheets on request
- Briefings & demonstrations for units & agencies
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