Terrance Dicks and producer Barry Letts, discussed the inspiration for the story, which came from Doctor Who and the Silurians and the involvement of in the story. Director Michael E. Briant discussed the direction of the story, the design of the Sea Devils and the inspiration for the design. Both Letts and Briant discussed Roger Delgado and his fear of water. Stuntman Stuart Fell discussed his involvement as both a Sea Devil and doubling for Katy Manning. Fell also talked about the Sea Devils coming out the water and the difficulties the stuntmen had while waiting for film the scenes.