Morning Departure

When British submarine Trojan sets off a magnetic mine at sea, the stern is obliterated and the vessel sinks to the ocean floor. Inside, a number of the crew are saved by watertight doors, but their air supply won't last forever. The captain, Lt. Cmdr. Armstrong (John Mills), releases some oil from the ship, and it's eventually spotted by a search party. As the necessary crew and equipment are brought in, it's a panicked race against time to get all the crew out alive.