Sleek

 were a race of eels. They could grow to large sizes and conduct electricity. (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 sleek it reset the planet to being healthy again. . (AUDIO: The Thief Who Stole Time)