Vengeance From The Deep

Vengeance From The Deep is the seventh episode of the tenth season of Doctor Who, and features the revival of the Sea Devils, last seen in tardis: Warriors of the Deep in 1984. It is the first part of a two part story arc, culminating in Red Sea.

Synopsis
"These monsters, they're not from space, they're not invading. They're reclaiming the planet, they were here first" - The Doctor

Back on Earth, several people have vanished at sea. They are all connected to the Sea V-2 program, a new scientific program to venture deeper below the ocean than ever before. But what they uncover is something the Doctor has seen before, the ancient masters of the Earth, sleeping for generations....