Sleek
From Tardis Wiki, the free Doctor Who reference
Sleek were a race resembling electric eels. They could grow to large sizes and conduct electricity. Sartia killed the "Great Sleek" on Funderell with a staser, committing deicide. (AUDIO: The Skin of the Sleek) They lived under the slow water and nipped at Romana II's feet. There was a giant Sleek for each timeline. When Blujaw Skaldson touched one of the giant sleeks it reset the planet to being healthy again. (AUDIO: The Thief Who Stole Time)