On July 26, 1945, the USS Indianapolis reached the island of Tinian, where it delivered the components and enriched uranium necessary for the atomic bomb Little Boy, which would soon devastate Hiroshima. But it's perhaps best known for its role in history's worst shark attack.
This incident may be burned in a lot of folks' consciousness thanks to Robert Shaw's monologue in Jaws, but the Smithsonian's Past Imperfect blog has a particularly excellent account of this harrowing historical incident. After leaving Tinian, the Indianapolis headed for Guam and then for the Filipino island of Leyte, where the crew was meant to receive training before continuing on to Okinawa. However, on July 30, the cruiser was struck by two Type 95 torpedoes fired by the Japanese submarine I-58. The Indianapolis crew sent distress call as the cruiser sank, but the calls were assumed to be a Japanese hoax, an attempt to lure out the American rescue boats. Nine hundred of the 1,196 men aboard the Indianapolis made it into the water alive; only 317 survived to see rescue. Up to 150 of the men died as a result of shark attacks.
What's particularly interesting about the Smithsonian piece are the details of this deadly incident. While many men suffered and died from exposure, thirst, salt poisoning, and their hallucinating fellows, sharks were attracted to the wreck by the corpses in the water. But sharks possess a lateral line, a sensory organ that allows them to detect movement, and the thrashing of the men in the water eventually attracted more and more sharks. Some of the survivors formed groups in the water, but they would quarantine men with open wounds who might attract sharks. When someone in the party died, it was imperative to shove their corpse away, so that the sharks might be sated on dead bodies instead of live ones.