Water beetle

Water beetle, any of a number of families of oval insects, in the order Coleoptera, that live in or near water and propel themselves by fringed hind legs. Three of the most common water beetles are the giant water scavenger beetle (family Hydrophilidae), predaceous diving beetle (family Dytiscidae), and whirligig (family Gyrinidae). The predaceous diving beetle and water scavenger beetle feed on small fish and insects.