James Caan

Cmdr. Richard Bolton, RNVR

David Sumner

Lt. Davies R.N.V.R

Norman Bowler

Sub-Lt. Pennington, RN

Paul Young

Leading Seaman Quentin

Brian Grellis

CPO Barquist X 3

William Dysart

Lt. Robert Talbot Gogan R.N.R.

John Kelland

Sub-Lt. Keith Willis, RNVR

Kenneth Farrington

CPO Boker Knowles

Carl Rigg

CPO Norman Kennedy

Steve Kirby

Leading Seaman X-2

Nick Tate

Leading Seaman X-1

George Pravda

Capt. Erlich of the 'Lindendorf'

Rupert Davies

Vice Admiral Redmayne (uncredited)

Keith Alexander

Sub. Lt. X-3

Diana Beevers

WRNS Officer (uncredited)

Paul Hansard

Cmdr. Steiner (uncredited)

Luke Hanson

German Lieutenant (uncredited)

Desmond Jordan

Naval Doctor (uncredited)

Dennis Mayers

Sub-Lieutenant on X-1 (uncredited)

Doug Robinson

Seaman in Self-defence Demonstration (uncredited)

George Roubicek

Redmayne's Flag Officer (uncredited)

Richard Steele

Captain in Redmayne's Office (uncredited)