Which beetles live in water?

Several families of beetles in the order Coleoptera are adapted to live in aquatic environments. These insects, collectively known as water beetles, include the following groups:

• Predaceous diving beetles: Members of the family Dytiscidae, these carnivorous beetles are highly adapted for swimming, with long, flattened, and fringed hind legs. They breathe by trapping a supply of air under their wing covers (elytra) while submerged.12
• Water scavenger beetles: Belonging to the superfamily Hydrophiloidea, these beetles typically inhabit marshy freshwater ponds. They are generally scavengers that feed on algae or decaying matter, though some species are predatory.32
• Other aquatic families: Several other beetle families have aquatic members, including whirligig beetles (Gyrinidae), crawling water beetles (Haliplidae), trout-stream beetles (Amphizoidae), screech beetles (Hygrobiidae), burrowing water beetles (Noteridae), and long-toed water beetles (Dryopidae).2

Additionally, some species of leaf beetles (Chrysomelidae) feed on the stems of freshwater plants, often living below the water level.4