Arthur Franz as Richard "Reef" Holloway

Dick Foran as Dan Wendover

Brett Halsey as Carl Neilson Jr.

Tom Conway as Ian Hunt

Paul Dubov as David Milburn

Bob Steele as "Grif" Griffin

Victor Varconi as Clifford Kent

Joi Lansing as Julie

Selmer Jackson as Admiral Terhune

Jack Mulhall as Justin Murdock

Jean Moorhead as Helen Milburn

Richard Tyler as Frogman Carney

Kenneth Becker as Frogman Powell

Sid Melton as Chester Tuttle

Frank Watkins as Watkins

Pat Michaels as Narrator

John Hilliard as Saucer Voice (voice)

Edmund Cobb as Passerby (uncredited)

Frank Lackteen as Passerby (uncredited)