In 1945, the Portland-class cruiser USS Indianapolis, commanded by Captain Charles McVay (Nicolas Cage), delivers parts of the atomic bomb that would later be used to level Hiroshima during the ending of World War II. While patrolling the Philippine Sea, on July 30, 1945, the ship is torpedoed and sunk by a Japanese submarine, taking 300 crewmen with it to the bottom of the Philippine Sea, while the rest climb out of the ship and are left stranded at sea for five days without food, water and left among shark-infested waters.
Without any hope for five days, most of the crew are eaten by sharks or die of salt-water poisoning by drinking sea water. On the 5th day, the crew are rescued by an airplane pilot who spots them by chance and calls for a rescue. Only 317 survive the disaster. Looking for a scapegoat for their own negligence, the navy court-martials and convicts Captain McVay for “hazarding his ship by failing to zigzag” despite overwhelming evidence supporting McVay.