VORCOOL Water-activated Electronic Mini Robotic Fish Toy Water-activated robotic fish: it will start to swim up and down when it's put into water Put the fish into the water tank, the fish is floating freely in the water. Its soft tail fin can be detachable, and also make life-like movements to propel the fish. Powered by 2 * LR44 button cells (included). Moving time: about 2 hours.