Hell Below
Tags: romantic

Plot synopsis:
When the commander of the United States Navy submarine AL-14 is wounded on its last cruise, Lieutenant Thomas Knowlton (Robert Montgomery), the second in command, hopes to be promoted and take his place. However, Lieutenant Commander T. J. Toler (Walter Huston) shows up and takes over.
Toler orders his officers to attend a ball. The young men dread having to dance with the wives of admirals, but Knowlton and his close friend and shipmate, Lieutenant Ed "Brick" Walters (Robert Young), are pleasantly surprised to discover the beautiful Joan Standish (Madge Evans) among the attendees. When an enemy air raid forces everyone to take shelter, Knowlton takes Joan to his apartment. Though she insists on leaving, he can tell she is attracted to him. However, before anything can happen, Toler shows up to collect his daughter.
On its next patrol, the AL-14 comes upon a German minelayer and hits it with torpedoes. After the Germans abandon ship, Toler sends Brick and a few men to search the sinking vessel for code books. When enemy fighters attack, Toler fights them off, but the arrival of a bomber forces him to leave his detachment behind. Knowlton disobeys his order and remains on deck, manning a machine gun, until he is knocked unconscious and carried below.
Upon returning to port, Knowlton goes to see Joan at the hospital. There he encounters patient Flight Commander Herbert Standish (Edwin Styles), Joan's disabled husband. Knowlton departs, but Joan follows him and confesses she loves him.
Back at sea, Toler tries to get Knowlton to break off the affair, to no avail. Toler has been ordered to merely map where new minelayers, now escorted by destroyers, are planting their mines. However, when Knowlton spots Brick's boat through the periscope, he imagines he sees his friend still alive. He countermands Toler's orders and attacks. Though several enemy ships are sunk, the sole surviving destroyer forces the AL-14 to dive to the sea bottom, 65 feet (20 m) below its maximum safe depth. After a while, Toler decides to surface, preferring to die fighting rather than suffocate. However, a crucial pump will not work. When it appears that they are doomed, one crewman commits suicide. Fortunately, repairs are made and the submarine surfaces, to find the enemy has departed. Eight crewmen are "down" as a result of Knowlton's actions.
He is courtmartialed and discharged from the Navy in disgrace. He and Joan plan to run away together, much to Toler's disgust. When Knowlton goes to the hospital to inform Joan's husband, he learns that a successful operation makes it likely that the man will recover fully. Knowlton puts on an act for Joan and her father, pretending to be so callous that she is repulsed.
Toler is given an extremely hazardous mission. To block the only port in the Adriatic from which German submarines can operate, the AL-14 is loaded with explosives and sent to ram a fortification beside the narrowest point in the channel out of the port. The rubble would block the exit. Knowlton sneaks aboard and reveals his ruse to Toler, who lets him stay. Under cover of a battleship bombardment, the AL-14 surfaces and heads in. The rest of the crew abandon ship as planned, leaving only Toler and Knowlton. Toler orders Knowlton over the side, but he pushes Toler overboard instead and steers the ship to its target, sacrificing his life.