Adults with chewing mouthparts, fore wings modified into a hard elytra, which covers the hind wings and usually most of the abdomen, antennae with 11 or fewer segments. Pupae are exarate, pads of forewings thickened, antennae with 11 or fewer segments, usually above water. Some adults are short-lived, some larvae take nearly a full year to complete their growth, a few take several years. There are normally 3 to 8 larval instars. The last instar larva usually leaves the water to find a pupation site.
Adults emerge and walk or fly to the water.
Adults may stridulate to attract mates. Eggs are usually laid in the habitat of the larvae and seldom diapause. All trophic roles are assumed by Coleoptera species. Many species are predacious, some with extra-oral digestion. Species from secondarily aquatic families often feed on aquatic vascular plants.