How Do Fish Swim

The method used by most fish to swim is to flap their bodies and tails in a sideways motion. On either side of the body of cartilaginous fish are two sets of paired fins. Above and below the mid line are plenty of single fins. These fish are not like bony fish and do not have a swim bladder filled with air to enable them to keep floating. Thus, they have to keep swimming or they will sink.

They may take short periods of rest, but are not able to go to sleep. Rays and skates stay near the bed of the sea and have flat bodies. Their enormous fins act like wings  and are used to keep themselves secure in the water as well as as for pushing themselves ahead in a forward motion.

Bony fish uses the muscles along their body to produce a side motion of the backbone in swimming. Fish push themselves sideways and backwards against the flow of water with the help of their tail and fins.

By rising and dipping it is able to steer itself and stop where required. Fins on the fishe's underside and back are used in steering in a fairly straight line and maintaining balance so that it does not wobble up and down or from one side to another.

Underwater creatures like the Eels have long fins on top and on the underside of their bodies and their movement resembles that of a snake. One of the curiosities of the water world is the flying fish. They can actually spread their front wing like fins, so that they can leap high, out of water as well as glide over it for many meters.