Commander P.J. Richardson (Gable) had his submarine sunk in the Bungo Straits by the Japanese destroyer Akikaze in 1942. Richardson, who survived the sinking but was reassigned to desk duty, is obsessed with the sinking of his ship, continually running war games to try and figure out what went wrong. Eventually he wrangles a posting as captain of the submarine USS Nerka. The Nerka's executive officer, Lt. Bledsoe (Lancaster) is none too happy about missing out on the chance to be CO of the Nerka himself. Tensions between Richardson and Bledsoe increase even further when Richardson tells his men that he's taking the Nerka back to the Bungo Straits, in search of the Akikaze, in direct defiance of Navy orders telling him to stay out of that area.
If not the Trope Maker for Hot Sub-on-Sub Action and other submarine warfare tropes in film, definitely a Trope Codifier. Loosely based on a novel by Real Life submarine commander Edward Beach. Other than the Dawson Casting of Gable and Lancaster—both decades too old to play sub officers—considered one of the more realistic depictions of submarine warfare, with effects that were cutting-edge for 1958.
Insult comic Don Rickles has a non-comic part as one of the crew.
- Action Prologue: The opening scene is Richardson's previous sub getting sunk by the Japanese.
- Artistic License Military: If a submarine is sunk while submerged, as was the case with Richardson's first boat, there's a nearly 100% chance it will go down with a loss of all hands. Of course, if it had, there wouldn't be a movie.
- Closed Circle: Everybody is confined to the Nerka while the plot plays out.
- Disc-One Final Boss: The Akikaze is destroyed quickly and without much of a fight during the final battle, only for it to turn out that it had a previously unknown submarine escort which proves to be a much greater threat.
- Dive! Dive! Dive!: Done realistically, and not in the panicked way that this line is often delivered in movies.
- Ending Memorial Service: Richardson's burial at sea ends the movie.
- Eureka Moment:
- When Bledsoe realized that the Japanese found the Nerka's trash, which allowed them to set up an ambush. This piece of information leads him to change his mind and execute Richardson's attack plan.
- Richardson has one of his own when he figures out the mysterious Morse transmission is coming from a Japanese submarine. Turns out it was a submarine, not the Akikaze, which sank his ship and the others lost in Bungo Straits.
- Hot Sub-on-Sub Action: Pretty realistically done. The Japanese sub twice fires torpedoes at the Nerka while underwater, and twice misses. When the Nerka finally sinks the Japanese sub, it does so while the Japanese sub is on the surface. Furthermore, the men of the Nerka are surprised that there's a sub attacking subs; it's completely unexpected.
- The Mutiny: Bledsoe relieves Richardson of command and orders a course back to Pearl Harbor. Until he changes his mind and goes back to the Bungo Straits.
- Pet the Dog: Commander Richardson, obsessed as he is, does have one nice moment. Namely, when a man is caught outside as the sub is diving and frantically pounding on the hatch loud enough for the crew to realize the situation, Commander Richardson instantly orders an emergency surface to save him from drowning.
- Reality Has No Subtitles: In the scenes that occur on the Japanese destroyer Akikaze or the unnamed Japanese submarine, none of the comments the Japanese naval officers make to each other are translated for the audience.
- Silent Running Mode: Done by both the crew of the USS Nerka and, later, by the Japanese submarine that was hunting them. This sets up a suspenseful sequence in which both the Nerka and the Japanese sub go quiet and even cut their engines, eventually drifting just past each other underwater.
- Tap on the Head: Averted. Richardson falls and hits his head during battle. This causes him to suffer recurring and prolonged blackouts that cause him to be relieved of command and he later dies of lingering internal injuries.
- The Smurfette Principle: Exactly one part for a woman—Richardson's wife, who appears in one scene at Richardson's home before the Nerka sets sail. Justified as women serving on subs wasn't exactly a thing back in WWII.
- Sub Story: One of the better ones.
- Time to Step Up, Commander: Lt. Bledsoe objects to Cmdr. Richardson's obsessive hunt for the Akikaze, as do his officers, who want Bledsoe to take command. After Richardson cracks his skull during combat, Bledsoe finally does take command, and he orders the Nerka back home. Gable, who was concerned with his super-macho screen image, insisted that Richardson be injured prior to being relieved of command.
- Tokyo Rose: The crew sometimes listens to her. A transmission from Tokyo Rose in which she identifies several of the crew by name tips off Bledsoe as to how the Nerka was tracked—the Japanese recovered their trash dumps.