The inversion is total. The bug's ventral surface, held uppermost in the water, is dark, while the dorsal surface facing down is pale, reversing the countershading of a normal animal and matching it to whichever background a predator sees. The eyes are oriented to watch the water below, and the animal detects prey partly through vibrations in the surface film above it.
Breathing works by a physical store rather than a lung. Hairs on the abdomen and under the wings hold a film of air taken at the surface, silver in appearance, from which the bug draws oxygen while submerged, returning periodically to renew it.
Backswimmers hunt actively, seizing mosquito larvae, other insects, tadpoles and occasionally small fish, then piercing them with the rostrum. The same beak causes the bite people receive from handling one, which is why the insect is known in some places as the water bee or water wasp.