There are approximately 2000 species of true water beetles native to lands throughout the world.
[2] Others have the surface of their exoskeleton modified to form a plastron, or "physical gill", which permits direct gas exchange with the water.
Some families of water beetles have fringed hind legs adapted for swimming, but most do not.
The scavenged material can come from aquatic vegetation, feces, or other small organisms that have died.
[5] The great diving beetle, a predator, feeds on things like worms, tadpoles, and even sometimes small fish.