First off - anytime I see someone post something from The Daily Mail, I know it's going to be crap. The only way you can get more bull**** on paper is to wipe a bull's arse with it.
Second, there's a big difference between a moving healthy diver at depth and several hundred possibly wounded, probably badly debilitated people floating on the surface. The big killers for the Indianapolis crew were exposure, salt poisoning, and dehydration. They were adrift for four days with little food or fresh water and no protection from the elements. Some actually lost their minds and killed other survivors. The sharks did take a number of crewmen alive, but in most cases they were scavenging corpses. That's what sharks do - they eat sick, injured, or dying animals. The Indianapolis gets the press because it was referenced in Jaws, but the same thing happened to a lot of ships that were sunk in the tropical latitudes during WWII.