Lake Monster

The Lake Monster was a species of flat, tentacled, predatory mutants with glowing eyes who existed on Skaro.

One Lake Monster lay deep in the Lake of Mutations and killed Elyon by pulling him beneath the water. (TV: "The Expedition") A Lake Monster in the petrified jungle was disturbed by the Doctor's TARDIS's return. (WC: A return to Skaro for the First Doctor...)