Meet Robo Terp 3: a bio-inspired robot that mimics the walking and swimming gaits of a terrapin. It has 3 DoF joints for faster and better mobility. Unlike other similar robots, Robo Terp is capable of swimming against the current. The rotational shoulder joint mimics a real turtle by allowing the robot to transition from swimming to walking.
The above video shows this robotic turtle in action. UMDRobotics has more on this robot.