Eel

An eel is an elongated fish that normally lives in the water. Most eels live in the shallow waters of the ocean and burrow into sand, mud, or amongst rocks. A majority of eel species are nocturnal, thus are rarely seen. Sometimes, they are seen living together in holes, or "eel pits". Some species of eels also live in deeper water on the continental shelves and over the slopes deep as 4,000 m (13,000 ft). Only members of the Anguilla regularly inhabit fresh water, but they, too, return to the sea to breed.

Mainstream Smurfs Media
In the Smurfs cartoon show, the evil witch Drusilla keeps a couple of eels as her pets inside a cave where she lives and guards her captive Manfred the Magnificent, who was transformed into a stone statue to prevent him from marrying Chlorhydris. These eels somehow have the ability to live on land instead of in the water.