From Mark Smiley:
This dynamic Lego Aquarium features fish that “swim” around the perimeter of the tank, a crab that jumps, and a starfish that spins as the fish pass by. This all happens by turning a crank which operates a smooth and robust mechanism built into the cabinet.
You can vote for the aquarium over at the LEGO Ideas website if you want to have it considered to become a real product!