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