Interest in fish swimming stems not only from the agility of certain species of fish and mammals in water but also from the fact that fish propulsion is so different from that of ships and submarines. Whereas these craft are designed to avoid unsteady motions as much as possible, fish employ rhythmic motions as their principal mode for swimming and turning. Recent studies have demonstrated that fish exploit unsteadiness to generate large, short-duration forces; coordinate the rhythmic unsteady body and tail motion to minimize the energy required for steady propulsion; and coordinate the motion of the body and tail to minimize the expended energy during maneuvering.