There is only one British species, Spercheus emarginatus (Schaller), formerly widespread in southeastern England but which is probably now extinct in the British Isles.  The beetle is 6mm long, largely medium brown to a paler yellow-brown, and the front of the head is deeply notched. It is usually found in ditches and stagnant water around the roots of aquatic plants, particularly reeds.  The aquatic larvae have obvious protuberant warts on the sides of the abdomen.