There's now at least a few robots that swim like fish, but they have their limits: they still take time to turn around, and they're not exactly precision instruments. Researchers at ETH Zurich are well on their way to solving those problems with their Sepios robot, though. As you'll see in the video below, the cuttlefish-inspired creation undulates its four fins in tandem to move in any direction, even through obstacles (such as seagrass and metal frames) that would trip up other animal-like automatons. It's quiet, too, so it can float near real fish without immediately causing a panic.
Sepios got its first real field test last year, and the ETH crew is now focused on getting the machine's sensors (including the camera, distance-measuring laser and depth sensor) to talk to each other more effectively. So long as development continues hiccup-free, this uniquely shaped rover and its successors could be very helpful for filming and studying undersea life without disturbing the very conditions you're trying to observe.