Swimming
Fish swim by exerting force against the surrounding water. There are exceptions, but this is normally achieved by the fish contracting muscles on either side of its body in order to generate waves of flexion that travel the length of the body from nose to tail, generally getting larger as they go along. The vector forces exerted on the water by such motion cancel out laterally, but generate a net force backwards which in turn pushes the fish forward through the water.
Most fishes generate thrust using lateral movements of their body & caudal fin. But there are also a huge number of species that move mainly using their median and paired fins. The latter group profits from the gained manoeuvrability that is needed when living in coral reefs for example. But they can't swim as fast as fish using their bodies & caudal fins.
Read more about this topic: Fish Locomotion
Famous quotes containing the word swimming:
“Mead had studied for the ministry, but had lost his faith and took great delight in blasphemy. Capt. Charles H. Frady, pioneer missionary, held a meeting here and brought Mead back into the fold. He then became so devout that, one Sunday, when he happened upon a swimming party, he shot at the people in the river, and threatened to kill anyone he again caught desecrating the Sabbath.”
—For the State of Nebraska, U.S. public relief program (1935-1943)
“Loosed betwixt eye and lid, the swimming beams
Of memory, blind school of cuttlefish,
Rise to the air, plunge to the cold streams....”
—Allen Tate (1899–1979)