The Sea Devils are a fictional race of amphibious reptilian humanoids. The Sea Devils, like their land-based cousins the Silurians, were scientifically advanced, and lived during prehistoric times in an aquatic civilization. At some point, the Moon approached close to Earth, threatening to cause geological upheaval, and both the Sea Devils and the Silurians went into self-induced hibernation to survive.
Appearance
Sea Devils look somewhat like humanoid turtles or plesiosaurs. They have beak-like mouths, large blue eyes, two fins on their head and a long neck. They are much more lizard-like than the Silurians and don’t have a third eye. They are as dextrous as humans and much better swimmers.
Sea Devils commonly wear a type of blue, gauze-like dress. The soldiers in Warriors of the Deep, on the other hand, wore thick armour somewhat reminiscent of samurai armour.
Overview
In their first appearance in the Third Doctor serial The Sea Devils, they were awakened from their hibernation by the renegade Time Lord known as the Master, who persuaded them to reclaim the planet from the human race. Despite the Doctor's efforts to convince them otherwise, the Sea Devils eventually decided to go to war, and the Doctor was forced to destroy their base. It was revealed, however, that there were many colonies still in hibernation around the world.
The Sea Devils next appeared in the 1984 serial, Warriors of the Deep, where they allied with the Silurians, in a second attempt to reclaim Earth from the humans. That attempt took place in 2084. Curiously, on that occasion the creatures used the terms "Silurians" and "Sea Devils" to refer to themselves, despite these terms previously being purely human phrases.
In general, they tend to be featured along with the Silurians in the spin-off media.