Robinson, a seasoned submarine captain, loses his job and sees an opportunity to redeem himself when an enigmatic backer finances a mission to recover a sunken Nazi U-boat rumored to be filled with gold, lying at the bottom of the Black Sea. Assembling a disparate crew of British and Russian sailors, Robinson balances tensions and mistrust, forged by years of Cold War enmity, while navigating the risky underwater terrain. The crew's differing motivations for taking part in the venture begin to threaten the mission's success, as Robinson strives to maintain order and focus on the goal of unearthing the treasure.

As the submarine ventures deeper into treacherous waters, technical problems, dwindling resources, and mounting paranoia escalate into chaos. Suspicions and greed among the crew members lead to volatile confrontations. The tense atmosphere is further exacerbated by the inherent dangers of underwater navigation and the constant threat of detection by enemy salvage operations. Robinson's leadership is put to the test as he confronts betrayal and the relentless pressures of survival, ultimately realizing that his dream of redemption may come at a far greater cost than he anticipated.