Adults from 14 families of aquatic or semiaquatic beetles from South Carolina are keyed and described: Gyrinidae, Haliplidae, Noteridae, Dytiscidae, Hydrophilidae, Hydraenidae, Scirtidae, Elmidae, Dryopidae, Limnichidae, Heteroceridae, Psephenidae, Ptilodactylidae, and Chelonariidae, including terrestrial forms in those families. These total 374 species in 96 genera that have been reported from or are likely to occur in this state. Included are diagnostic diagrams to aid in keying, a photograph of one species from nearly each genus, data on range both in South Carolina and in North America, and months of collection in South Carolina. Thirty-nine new state records are noted.