We shall destroy man and reclaim the planet.
~ The Chief Sea Devil to the Doctor

The Chief Sea Devil is an antagonist from the Doctor Who episode The Sea Devils. He along with other Sea Devils lived in the waters of Earth during the prehistoric times along with their land cousins the Silurians and when humans were still apes.

Sometimes in the 1970s, the Chief along with his group of Sea Devils where awoken from hibernation by The Master who wished for them to rule Earth again. The Third Doctor traveled to the Sea Devil's underwater base and tried to convince the Chief that the Sea Devils could co exist with humans, but the Master arrives and reveals that the Doctor failed to make a peace treaty with the Silurians and they were killed.

The Chief agrees to the peace treaty, but changes his mind when the base is shot at by the navy and orders for the Doctor to be killed and later turns on the Master too. Luckily, the Doctor and the Master escape and leave behind an explosive device that destroys the base, killing the Chief and the other Sea Devils.