The original script had Jamie defeating the seaweed by playing his bagpipes.
This episode was wiped by the BBC and no copy of it is known to exist.
This episode was watched by 6.9 million viewers on its original transmission.
This episode takes place in England in 1968.
The Doctor claims to have learned how to fly a helicopter by observing Astrid Ferrier. That incident took place during the previous adventure, "The Enemy of the World."