The USS Indianapolis was torpedoed by a Japanese ship after it delivered atomic bomb parts to Tianan Island in July of 1945. Almost 300 men died in the attack, but 900 were left floating in the water. The ship had no escort, and intercepted Japanese reports of the sinking were considered to be a ruse.
The first night, the sharks focused on the floating dead. But the survivors’ struggles in the water only attracted more and more sharks, which could feel their motions through a biological feature known as a lateral line: receptors along their bodies that pick up changes in pressure and movement from hundreds of yards away. As the sharks turned their attentions toward the living, especially the injured and the bleeding, sailors tried to quarantine themselves away from anyone with an open wound, and when someone died, they would push the body away, hoping to sacrifice the corpse in return for a reprieve from a shark’s jaw. Many survivors were paralyzed with fear, unable even to eat or drink from the meager rations they had salvaged from their ship. One group of survivors made the mistake of opening a can of Spam—but before they could taste it, the scent of the meat drew a swarm of sharks around them. They got rid of their meat rations rather than risk a second swarming.
But the sharks weren't the only danger for those stranded in the sea. Of the 1,196 men on the Indianapolis, only 317 were rescued alive. Read the rest of the story at Smithsonian. Link