As Shaw's character put it, "Very first light, Chief, sharks come cruisin'."
1,196 men were on the ship; about 900 survived the sinking, and the sharks took almost six hundred of them. The survivors had no, or almost no, provisions, and many of them suffered injuries, including painful burns, during the sinking of the ship. I think what makes the Indianapolis story such a shocker is that it combines horrors you wouldn't think go together: war and predatory animals. It sounds like an implausible nightmare, but it really happened.
File under "things you randomly find online:" I didn't know that the Japanese Army suffered its own Indianapolis-type event during World War II. The horrors were of a shorter duration, but many more men died. Enough to put in it the Guinness Book of World Records:
Most Deaths Caused By Crocodiles
The crocodile attack to claim the most human lives took place on February 19, 1945, when an Imperial Japanese Army unit guarding a stronghold on the Burmese island of Ramree was outflanked by a British naval force. The soldiers were forced to cross 16 km (10 miles) of mangrove swamps to rejoin a larger battalion of the Japanese infantry. The swamps were home to thousands of 4.6-m (15-ft) saltwater crocodiles. Come the next morning, only 20 of the 1,000 Japanese soldiers had survived.
Think about that sometime, when you're trying to get to sleep at night. If, you know, you don't *want* to sleep. Or if you're trying to come up with an idea for a horror movie.
UPDATE: More info here; apparently there's some controversy over whether it's true. That settles it: this *should* be a horror movie.