Fish have a variety of different body plans. At the broadest level, their body is divided into head, trunk, and tail, although the divisions are not always externally visible. The body is often fusiform, a streamlined body plan often found in fast-moving fish. They may also be filiform (eel -shaped) or vermiform (worm-shaped).

A fish is shaped for where it lives and how it feeds. A fish with a torpedo shape can swim quickly through the water. A fish that is flat can easily hide on the bottom of the water. Some fish are shaped like eels. Some fish have long shovel-shaped or paddle-shaped snouts. Other fish such as gar are spear-nosed.