The Mediterranean, 1941/42 - Axis forces are using frogmen and manned torpedoes to attack previously impregnable harbours. The Allied forces need to come up with something to answer this threat, which they find in the form of Lt. Lionel "Buster" Crabb.

Laurence Harvey
as Lieutenant "Buster" Crabb, R.N.V.R.

Michael Craig
as Leading Seaman Knowles

Dawn Addams
as Third Officer Jill Masters, W.R.N.S

John Clements
as The Admiral

Sidney James
as Chief Petty Officer Thorpe

Alec McCowen
as Able Seaman Morgan

Nigel Stock
as Able Seaman Fraser

Ian Whittaker
as Ordinary Seaman Thomas

Arnoldo Foà
as Tomolino

Gianna Maria Canale
as Conchita