True eels (Anguilliformes) are an order of fish, which consists of four suborders, 19 families, 110 genera and approximately 600 species. Most eels are predators.
The flat and transparent larva of the eel is called a leptocephalus. A young eel is called an elver.
Most eels prefer to dwell in shallow waters or hide at the bottom layer of the ocean, sometimes in holes. These holes are called eel pits. Only the Anguillidae family comes to fresh water to dwell there (not to breed). Some eels dwell in deep water (in case of family Synaphobranchidae, this comes to a depth of 4,000 metres (13,000 ft), or are active swimmers (the family Nemichthyidae - to the depth of 500 metres (1,600 ft)).
