The Great Diving Beetle is a large water beetle, with a generally dark brown/black appearance and orangey-brown margins to the elytra and thorax. The male beetle is general has a smooth and shiny, with females having noticeable grooves during both the laval and adult stages. Both adults and larvae lack gills and have to surface for air: adults store a small supply of air under their elytra.
The Great Diving Beetle is relatively common and widespread throughout the British Isles.
Great Diving Beetles are usually found in ponds and lakes with good amounts of vegetation.
Both adult beetles and larvae are active predators, feeding on other freshwater insects, crustaceans, snails, tadpoles and even small fish. The larvae have hollow jaws with which they suck up the juices of their prey.