Germany based ETH Zurich is currently working on its second generations naro-tartaruga, a robotic sea turtle. They have chosen to use this as a model because its rigidity is simpler than a fish. The largeness of the body houses sensors and batteries used to make it autonomous. Its fin actuators work independently of each other and of course the turtle is waterproof. We don't know much about the science but we do know this robotic creature can certainly swim in a very kewl way.