Additional information (Wiki): True eels are elongated fishes, ranging in length from 5 centimetres (2.0 in) in the one-jawed eel (Monognathus ahlstromi) to 3.75 metres (12.3 ft) in the giant moray. They possess no pelvic fins, and many species also lack pectoral fins. The dorsal and anal fins are fused with the caudal or tail fin, to form a single ribbon running along much of the length of the animal. Most true 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 members of the Anguillidae family regularly inhabit fresh water; they too return to the sea to breed. Some eels dwell in water as deep as 4,000 metres (13,000 ft). Others are active swimmers. Eels begin life as flat and transparent larvae, called leptocephali. Eel larvae drift in the surface waters of the sea feeding on small particles called marine snow. Eel larvae then metamorphose into glass eels and then become elvers before finally seeking out the adult habitat.