The forelegs are relatively long and often held forward. They are easily recognized by the erratic swimming behavior on the surface of the water. There are a number of aquatic beetles that have the same general body shape. The separated eyes of Gyrinidae are characteristic of adults. Pupation occurs in cocoons on plants or on the shore.
Mouthparts are for chewing.
These beetles often congregate in both flowing and still water, especially streams and ponds. Adults feed on organisms on the surface of the water or scavenge debris. They spend much of their life on the surface of water. Some Dineutus species can secrete a milky substance which emits an odor that resembles ripe apples while Gyrinus species emit an unpleasant odor. They can swim rapidly.