There are 19 families and over 400 species in this order. Eels have long, scaleless, snake-like bodies. They don’t have pelvic fins and their pectoral fins are either very small or nonexistent. They have long anal and dorsal fins. If they have a caudal fin, it joins in a continuous line with the dorsal and anal fins.

Eels are found in fresh and salt water habitats, but most species are found in salt water habitats. Female eels lay eggs.