The ship you mention was the USS Indianapolis. It was torpedoed just after delivering parts for the first atomic bomb. 300 of the 1200 crew went down with the ship. The other 900 were left in the water where a shark feeding frenzy picked sailors off. Only 317 would survive. Its biggest single loss by the US Navy and largest mass shark attack. The captain in Jaws mentions the attack which he was part of (as written in script)
http://en.wikipedia.org/wiki/USS_Indianapolis_%28CA-35%29
One thing about sharks I learned first hand was that their colours are different from photos of captured sharks. My hammerhead wasn't grey in the water but a beautiful light green-yellow. I also saw captured dolphins (not porpoises but dolphins) lose their colour when taken into the boat. When they jumped out of the water while on the line they looked like rainbows. That all went away once taken from the water.