Great diving beetle
Dytiscus marginalis
The great diving beetle, Dytiscus marginalis, is a large aquatic diving beetle native to Europe and northern Asia, and is particularly common in England. The great diving beetle, true to its name, is a rather sizable insect. The larvae can grow up to 60 millimetres (2.4 in) in length, while the adults are generally between 27–35 millimetres.