Pescaton

Pescatons were a technologically advanced race of shark-like humanoids. They were significantly taller than Humans, having the head, body and texture of a shark, very sharp teeth, clawed fins, and webbed feet. They were cunning, ravenous, and ferocious, attacking and feeding on anything that came in their path. Although their steel-like skin made them invulnerable to conventional weapons, they could be killed by either long periods out of salt water or prolonged high-pitched noise, after which their flesh disintegrated, leaving behind their vertebrae.

The Doctor first encountered the Pescatons on their dying home world in the 15th century. Their leader, Zor, had brought him there to help them find a new planet. The Doctor refused, defeated Zor in mental combat, and escaped back to the TARDIS.

In the late 20th century, the Pescatons invaded Earth, attacking and killing many people in London. The Doctor and Sarah Jane Smith discovered their weakness to high-pitched noise and set a trap for Zor, killing him. When he died, all the other Pescatons died as well. (Doctor Who and the Pescatons)