The world's first operational atomic bomb was delivered by the Indianapolis, (CA-35) to the island of Tinian on 26 July 1945. The Indianapolis then reported to CINCPAC (Commander-In-Chief, Pacific) Headquarters at Guam for further orders. She was directed to join the battleship USS Idaho (BB-42) at Leyte Gulf in the Philippines to prepare for the invasion of Japan. The Indianapolis, unescorted, departed Guam on a course of 262 degrees making about 17 knots.
At 14 minutes past midnight, on 30 July 1945, midway between Guam and Leyte Gulf, she was hit by two torpedoes out of six fired by the I-58, a Japanese submarine. The first blew away the bow, the second struck near midship on the starboard side adjacent to a fuel tank and a powder magazine. The resulting explosion split the ship to the keel, knocking out all electric power. Within minutes she went down rapidly by the bow, rolling to starboard.
Of the 1196 aboard, about 900 made it into the water in the twelve minutes before she sank. Few life rafts were released. Most survivors wore the standard kapok life jacket. Shark attacks began with sunrise of the first day and continued until the men were physically removed from the water, almost five days later.
Shortly after 11:00 A.M. of the fourth day, the survivors were accidentally discovered by LT. (jg) Wilbur C. Gwinn, piloting his PV-1 Ventura Bomber on routine antisubmarine patrol. Radioing his base at Peleiu, he alerted, "many men in the water". A PBY (seaplane) under the command of LT. R. Adrian Marks was dispatched to lend assistance and report. Enroute to the scene, Marks overflew the destroyer USS Cecil Doyle (DD-368), and alerted her captain, of the emergency. The captain of the Doyle, on his own authority, decided to divert to the scene.
Arriving hours ahead of the Doyle, Marks' crew began dropping rubber rafts and supplies. While so engaged, they observed men being attacked by sharks. Disregarding standing orders not to land at sea, Marks landed and began taxiing to pick up the stragglers and lone swimmers who were at greatest risk of shark attack. Learning the men were the crew of the Indianapolis, he radioed the news, requesting immediate assistance. The Doyle responded she was enroute.
As complete darkness fell, Marks waited for help to arrive, all the while continuing to seek out and pull nearly dead men from the water. When the plane's fuselage was full, survivors were tied to the wing with parachute cord. Marks and his crew rescued 56 men that day. The Cecil Doyle was the first vessel on the scene. Homing on Marks' PBY in total darkness, the Doyle halted to avoid killing or further injuring survivors, and began taking Marks' survivors aboard.
Disregarding the safety of his own vessel, the Doyle's captain pointed his largest searchlight into the night sky to serve as a beacon for other rescue vessels. This beacon was the first indication to most survivors, that their prayers had been answered. Help had at last arrived. Of the 900 who made it into the water, only 317 remained alive. After almost five days of constant shark attacks, starvation, terrible thirst, suffering from exposure and their wounds, the men of the Indianapolis were at last rescued from the sea.