The Sea Devils are a race of humanoid reptillain species in Doctor Who. They are also the cousins of the Silurians
The Sea Devils
An amphibious variety of Silurians were awakened from their hibernation by a renegade Time Lord known as the Master (Roger Delgado), 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, forcing the Doctor to destroy their base. It was revealed, however, that there were many colonies still in hibernation around the world.
Warriors of the Deep
The land-based Silurians and the 'Sea Devils' next appeared, together, in Warriors of the Deep (1984), where they attempted again to reclaim Earth from the humans. Set in the year 2084 during a prolonged "cold war" between factions of humanity. The Sea Devils in this episode were described as being elite warriors; they sported bullet-proof samurai-style armour. The Fifth Doctor (Peter Davison) tries in vain to prevent any bloodshed against either species; he tells companions Tegan (Janet Fielding) and Turlough (Mark Strickson) to give the Silurians oxygen to keep them safe from the hexachromite gas he released into the base's atmosphere. The last surviving Silurian in the episode, however, is killed by Turlough, leaving the Doctor despondent