Cast
George O'Brien
Cmdr. Robert 'Bob' Kingsley
Walter McGrail
Chief Joe Cobb
Jack Murphy
Naval Reservist (uncredited)
Ferdinand Schumann-Heink
Adolph Brucker (uncredited)
Walter C. Kelly
Chief Mike 'Guns' Costello
Warren Hymer
'Lug' Kaufman
Joseph Depew
Naval Reservist (uncredited)
Henry Victor
Baron Ernst von Steuben (U-boat commander)
George Harris
Naval Reservist/Swimmer and Diver (uncredited)
Nat Pendleton
'Butch' Wagner (uncredited)
Larry Kent
Lt. 'Mac' McGregor
Maurice Murphy
Merkel (uncredited)
John Loder
Franz Shiller
Harry Strang
Gunner and drill sergeant (uncredited)
Marion Lessing
Anna Marie Von Steuben
Mona Maris
Fraulein Lolita
Francis Ford
Eric - Captain of Trawler (uncredited)
Hans Fuerberg
Fritz Kampf (Second Officer of U-172) (uncredited)
Edward Peil Jr.
Naval Reservist (uncredited)
Harry Tenbrook
Winkler (uncredited)
Steve Pendleton
Ens. Richard 'Dick' Cabot (as Gaylord Pendleton)
William Collier Sr.
Mugs O'Flaherty (uncredited)