Thunder Afloat

John Qualen

Milo

Regis Toomey

Ives

Henry Victor

German U-Boat Officer

Addison Richards

Admiral Ross

Hans Joby

U-Boat Petty Officer

Henry Hunter

Ensign Dyer

Jonathan Hale

Admiral Girard

Leon Ames

Recruiting Officer (uncredited)

Arthur Belasco

Fisherman (uncredited)

Joseph E. Bernard

Fisherman (uncredited)

Wade Boteler

Recruiting Officer (uncredited)

Al Bridge

Fisherman (uncredited)

Rand Brooks

Listener (uncredited)

Don Castle

Radio Operator (uncredited)