There are about 400 species in six families within this order of fish found in oceans around the world.

Some species are found in the abyssal (deep-sea) zone, while others live in shallow waters, especially near coral reefs. A few even inhabit freshwater environments. Although most species live in tropical and subtropical regions, some can be found as far north as the coast of Greenland.

Ophidiiformes feed on small fish, crustaceans, and other tiny animals they find along the seafloor. These fish usually have small heads and long, slender bodies, with a dorsal (top) fin that runs along much of their body and an anal fin that merges with their caudal fin (tail fin). Their bodies may have smooth scales or no scales at all.

Most species live near the ocean floor, where they hide in sand, mud, or rocky crevices. Others live in the deep ocean, where conditions are dark and cold.