Sinking of the USS Indianapolis?
On TV, about 30 years ago, I caught the last half or third of an old black and white film that I haven't been able to track down. I'm guessing it was set sometime in WWII. Based on the production style, I'm guessing it was filmed in the '50s or early '60s.
From when I started watching to the end, hundreds of sailors were floating in the sea, in small clusters. Seemed like pretty much all of them were in life vests or life rings. Maybe a few groups had a small lifeboat. Swimmers would report to the captain and then swim back to the clusters to relay his messages/orders. At one point, maybe a few points, sharks attacked.. At the end, rescuers arrive and one sailor swims over to his buddy to wake him up and tell him they'd be found. His buddy slumps into the water. He may have been missing his legs at that point, implying that a shark had taken a big bite out of him.
Ring any bells?