Here is another robot inspired by nature that can swim under water without causing major disturbance. Developed by engineers and marine biologists at the University of California, this robot can swim silently in salt water without an electric motor. It uses artificial muscles filled with water to move.
This foot long robot is connected to an electronic board that is stored above the surface. As the researchers explain:
The bot is equipped with cables that apply voltage to both the salt water surrounding it and to pouches of water inside of its artificial muscles. The robot’s electronics then deliver negative charges in the water just outside of the robot and positive charges inside of the robot that activate the muscles. The electrical charges cause the muscles to bend, generating the robot’s undulating swimming motion. The charges are located just outside the robot’s surface and carry very little current so they are safe for nearby marine life.