The USS Indianapolis was torpedoed and sunk.
The officer in charge of monitoring her movements never reported that she was late. Of the three stations that received her distress call, one commander was drunk, one had ordered his men not to wake him up and the third thought it was a Jap deception.
The men were in the water for nearly four days before they were spotted by a patrol plane. Other airplanes came. One PBY pilot disregarded orders and landed to rescue survivors. The USS Cecil J. Doyle came, shining a searchlight against the clouds, to give the survivors in the water hope that they would be rescued.
Fully two-thirds of the men who had survived the sinking perished while awaiting rescue. Everyone expected to lose ships during wartime and, if rescue had been prompt, the loss of the Indianapolis would have been filed under "shit happens during war". But to not know she was lost and to have the survivors in the water to be feasted upon by sharks for days was beyond horror.
The Navy revamped the MOVREP system.
The CO of the Indianapolis, Captain McVay, was court-martialed in a Navy cover-up of a type that was not seen until the turret explosion on the USS Iowa. He was eventually exonerated, though that finally happened decades after he took his own life.