Among them is the infamous story of the USS Indianapolis. After delivering crucial components of the atomic bomb that would level Hiroshima in 1945, the Indianapolis was sunk by a Japanese submarine in the South China Sea. Of the nearly 1,200 men aboard, 900 survived the torpedoing, spilling into the sea. Whitetip sharks began attacking the next morning, and after 4 days only 300 sailors were still alive.
Less well known are the stories of other ships sinking in shark-infested waters, with similar gruesome results. There is the case of the Cape San Juan, a U.S. troop transport ship that was torpedoed near the Fijian Islands. Nearly 700 of the survivors were killed by sharks.
Yet another horrifying event involved the HMS Birkenhead, which sank off Danger Point, South Africa, in 1852, resulting in 440 shark-related fatalities.
The above true incidents and many others are described in well-researched and gory detail in Unspeakable Horror.