In 1915, Captain Liers, commander of a submarine is leaving his hometown, where he, his 2nd officer and the radio-operator, who is married there, spend their shore leave. Liers two brothers were already killed in action, so his mother doesn't like the idea of him going back to his sub. Liers thinks his 2nd officer is in love with a local girl, who is really pining for him. On patrol they sink a British armoured cruiser, but while returning to their harbor, they're attacked by a sub trap. They're able to sink it, but the trap has alarmed a destroyer, that sinks their sub. The sub lays on the sea bed at 200 feet, and except for the bridge, it is full of water. 10 members of the crew survived, but there are only 8 rescue devices. Liers gives the order, that the crew shall use them, but they disobey, either all get out or nobody...
