This children's fantasy tells the story of a 12-year-old boy who discovers a complex underwater world where young children are held prisoner by an evil shark and an eel.

Director: Lionel Jeffries

Cast: James Mason, Bernard Cribbins, Billie Whitelaw, Joan Greenwood, David Tomlinson, Tommy Pender, Samantha Gates, Paul Luty, Jon Pertwee, Olive Gregg, Lance Percival, David Jason, Cass Allan, Liz Proud, Una Stubbs