- John Mills
- Captain - Lt. Taylor, R.N.
- Louis Bradfield
- First Officer - Lt. Brace, R.N.R.
- Ronald Millar
- Third Officer - Lt. Johnson, RNVR
- Jack Watling
- Navigating Officer - Lt. Gordon, R.N.
- Reginald Purdell
- Coxwain - C / P.O. Dabbs
- Caven Watson
- Chief Engine Room Artificer - C / P.O. Duncan
- Niall MacGinnis
- Torpedo Gunner's Mate - C / P.O. Mike Corrigan
- Eric Portman
- On Hydrophones - L / S. Hobson
- Leslie Weston
- Leading Torpedo Operator - L / S Tug Wilson
- Norman Williams
- Periscope Operator - 'Canada'
- Lionel Grose
- Torpedo Operator - 'Spud'
- David Peel
- Helmsman - 'Oxford'
- Philip Godfrey
- Steward - 'Flunkey'
- Robert Wilton Jnr
- Cook - 'Pincher'
- Marie Ault
- Mrs. Metcalfe
- Victor Beaumont
- German Airman
- Franklyn Bennett
- (uncredited)
- Frederick Burtwell
- Sidney Briggs
- George Cross
- (uncredited)
- Kenneth Evans
- (uncredited)
- Ian Fleming
- Captain
- Philip Friend
- Humphries
- Walter Gotell
- Luftwaffe Captain
- Pat Hagan
- Submariner
- Vincent Holman
- Danish Captain
- Joan Hopkins
- Ethel Dabbs
- Mike Johnson
- ARP Man at Wedding
- Molly Johnson
- (uncredited)
- Vi Kaley
- Old Lady in Chip Shop
- Olaf Olsen
- Luftwaffe Airman
- Bryan Powley
- (uncredited)
- John Salew
- Drake
- Gerik Schjelderup
- (uncredited)
- Johnnie Schofield
- Policeman in Chip Shop
- Ian Selby
- Man in Health Club
- John Slater
- Charlie
- Joan Sterndale-Bennett
- (uncredited)
- Vi Stevens
- Publican's Wife
- Merle Tottenham
- (uncredited)
- David Trickett
- Peter Hobson
- Robert Brooks Turner
- Trawler Captain
- Beatrice Varley
- Mrs. Dabbs
- Ben Williams
- Messenger
- Ian Wilson
- Cigarette Customer
- Josephine Wilson
- Alice Hobson
