John Berman snorkels with a marine biology teacher and whale sharks. A journalist from the U.S. television channel ABC was almost swallowed by a whale shark underwater when he attended a meeting with the animal. John Brenan was frightened when the whale shark approached him from behind and was preparing to swallow, reports the ABC. The American, upon leaving the water, the sharks described as very fast, but very quiet and were relieved not to have been a great white shark approaching from the rear. The whale shark, the largest in the world feeds on crustaceans, plankton and shoals, and experts agree that it can reach 15 or 20 feet and weigh over 10 tons, not presenting a danger to humans.