Clive Brook as Captain Tom Armitage

John Clements as Lieutenant Cranford

Edward Chapman as Captain Eckersley

Judy Campbell as Lucy Armitage

Penelope Dudley-Ward as Mabel

Edward Rigby as Mr. Matthews

Allan Jeayes as Commander Blount

Michael Wilding as Dot

Harold Warrender as Lt. Commander Martin

David Hutcheson as Captain Sandeman

George Carney as Bates

Al Millen as Knowles

Charles Farrell as Walker

John Laurie as Gates

George Benson as Parker

Hay Petrie as Minesweeper Skipper

Mervyn Johns as His Mate

Albert Lieven as Commander U.37

John Wengraf as Commander Deutschland

Edward Lexy as Merchantman Skipper

John Glyn-Jones as Mate

John Boxer as German Captain

John Carol as Edmonds

Alec Clunes as Bit Part

Anton Diffring as U-Boat Officer

Derek Elphinstone as Hawkins

Alf Goddard as Bosun's Mate

Stewart Granger as Sutton

Bryan Herbert as Signals Yeoman

Patrick Holt as Holt

James Knight as Admiral

Maire O'Neill as Mary Hogan

Charles Rolfe as Peacock - Wardroom Steward

Harry Terry as Sailor

Charles Williams as 'Shorty' Howard

Howard Lang as Gunnery Officer (uncredited)