This serial was the first Doctor Who story to involve the Royal Navy in production, as opposed to the Army in previous episodes. When the RN was approached, the production crew was invited to shoot during naval exercises. It proved a mutually beneficial arrangement: the RN got excellent publicity for their participation, while the production received free access to Naval facilities, ships and equipment with a large number of military personnel as volunteers eager to appear on television. The fact that the then current series star, Jon Pertwee, was a veteran naval officer himself resulted in very pleasant encounters with the sailors eager to meet him.
This episode was watched by 9.7 million viewers on its original transmission.