December 1943. America’s underwater forces fight to sink Japanese ships as the enemy’s anti-submarine measures grow more deadly. Richard Hetherington O’Kane assumes command of USS Tang, a new breed of submarine engineered to dive 150 feet deeper than previous builds. As Tang prepares for its first patrol, O’Kane learns that mentor and friend Dudley “Mush” Morton is missing and presumed lost aboard his submarine USS Wahoo.
Driven to avenge Morton’s loss, O’Kane hits the South Pacific with fury. In Tang’s first four patrols its fiery commander transits 40,000 miles and sinks 17 ships, climbing to the rank of America’s top submarine ace. Shortly after surviving an epic depth charge off the coast of Japan, Navy brass sends Tang to the Formosa Strait to hound maritime traffic as Allied forces bomb Japanese airfields on the island now known as Taiwan.
Armed with the U.S. military’s new Mark 18 torpedoes, O’Kane and his crew attack escalating targets, thwarting menacing escorts rigged to sink them. On October 25th, 1944, Tang ambushes a 12-ship convoy, firing nine of its eleven remaining warheads before its commander is driven away by a submarine-hunting warship. But looking back on the carnage O’Kane discovers that one of the ships Tang torpedoed hasn’t sunk. Fueled by the same drive as his mentor Morton, O’Kane heads back into the fray with Tang’s last two torpedoes to finish what he started.
At 2:30 a.m. Tang fires its final Mark 18 torpedo at the crippled ship in a bid to make sure the enemy hits the bottom. In a horrific twist the warhead goes rogue and circles back striking O’Kane’s submarine. As Tang sinks to the bottom of the Formosa Strait, what’s left of its crew wages an unforgettable fight to survive.