The giant water bug is the largest aquatic insect in Quebec. Its flat, hydrodynamic body and the long hairs on its middle and back legs make it a fast and efficient swimmer. It has large compound eyes on its head. It eats using piercing-sucking mouthpieces that form a sort of short, pointed beak, called a rostrum, under its head. It has a short respiratory tube at the end of its abdomen that consists of two flexible, retractable parts that can move back and forth.