Cuttlefish are fascinating animals, in that they use a pair of undulating fins to move forward and backward, turn on the spot, or hover in place. If you wanted to make an underwater robot that was highly maneuverable yet quiet and immune to tangled propellers, then the cuttlefish would be a good creature to copy. Well, a group of mechanical engineering students from Switzerland's ETH Zurich have done just that – plus they gave it an extra set of fins, allowing it to also move straight up and down.

Known as Sepios, the robot was first revealed to the public last May.

Each of its four fins contain nine rays, each one of which has a 270-degree range of motion, and is activated by its own servo motor. Those fins join onto a central body that contains a mechanical swim bladder, which allows the robot to maintain a given depth by adjusting its buoyancy.

Other bits and pieces in that body include (or will eventually include) a live-streaming video camera, a water pressure/depth sensor, laser distance-measuring hardware, and a bundled accelerometer, gyroscope and magnetometer, which are used for attitude control. The whole robot tips the scales at 22.7 kg (50 lb).

Sepios can move in any direction, thanks to its four bio-inspired undulating fins

One charge of the robot's battery pack allows it to operate for a quite respectable 90 minutes, descending a maximum of 10 meters (33 ft).

Because of its stealth and maneuverability, the team has suggested that Sepios could be particularly well-suited to observing and filming marine life. You can see the robot in action, in the video below.

For another example of an underwater robot that utilizes an undulating fin, check out Northwestern University's black ghost knife fish-inspiredGhostBot.

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