Captain Casey Abbott commands an American submarine in the Pacific during World War II. When a perilous mission to retrieve a new Japanese mine for study goes awry, he's forced to abandon a likable combat diver. Abbott's orders to leave a man behind appear to be justified, but his second-in-command believes he had ulterior motives:
| Actor | Role |
|---|---|
 Ronald ReaganCmdr. Casey Abbott (Captain, USS Starfish) | Cmdr. Casey Abbott (Captain, USS Starfish) |
 Nancy ReaganNurse Lt. Helen Blair | Nurse Lt. Helen Blair |
 Arthur FranzLt. Cmdr. Don Landon (XO, USS Starfish) | Lt. Cmdr. Don Landon (XO, USS Starfish) |
 Robert ArthurFreddy Warren | Freddy Warren |
 William LeslieLt. Paul Prentice | Lt. Paul Prentice |
 William PhillipsCarroll (as William Phillips) | Carroll (as William Phillips) |
 Harry LauterLt. (j.g.) Wes Barton | Lt. (j.g.) Wes Barton |
| MMichael GarthBill aka Lt. Charlie | Bill aka Lt. Charlie |
 Joe TurkelChick (as Joseph Turkel) | Chick (as Joseph Turkel) |
 Don KeeferJug | Jug |
 Chester W. NimitzHimself (in prologue) (uncredited) | Himself (in prologue) (uncredited) |