A German U-boat, U-96, embarks on a patrol mission during World War II, manned by a young, inexperienced crew led by a seasoned captain. The film captures the crew’s initial excitement and anticipation of battle, which is quickly tempered by the harsh realities of life at sea. The tight, claustrophobic conditions aboard the submarine serve as the backdrop for character development, as the men bond, clash, and cope with the tedium of long stretches of inactivity punctuated by moments of intense combat and crisis. The narrative explores the tension between the young war correspondent aboard, who represents the idealistic views of the German public, and the wearied perspectives of the captain and his veteran crew, who are acquainted with the brutality of war.

As the U-boat ventures into the Atlantic, it encounters enemy forces and the crew is forced to engage in a deadly game of cat-and-mouse with an ever-present threat of discovery and attack by Allied destroyers. The crew's skill and the captain's tactical acumen are tested as they navigate underwater minefields, depth charge assaults, and mechanical malfunctions. The cramped, oppressive environment intensifies emotions and the psychological strain takes its toll. With each engagement, the true cost of war becomes more evident and the initial romanticism of adventure is replaced by a desperate will to survive the ordeals of battle and the unforgiving ocean.