The Doctor is taken to the Sea Devils' underwater colony where he tries to make peace with the creatures, only for the navy to attack the base.
Did You Know?
This episode was watched by 8.3 million viewers on its original transmission. See more
The Rear Admiral wears several World War One medal ribbons. Somebody old enough to have served in WWI would be well past military retirement age in 1972. See more
The BBC wish to acknowledge the help given to them by the Royal Navy in the making of this programme See more