At 65 feet (20 meters), the whale shark is the largest fish on Earth, yet is harmless to humans. Like its namesake the blue whale, the whale shark is a filter feeder, straining plankton out of the water. Bristles along its gill slits filter water that flows through the shark's mouth and trap tiny organisms that it feeds on.
In some areas, such as Western Australia, a tourist industry has grown up around whale sharks, with a small number of companies licensed to take customers on dives with sharks. Some people have objected to the practice, as its impact on the sharks is not certain.
Photograph by Kennan Ward/CORBIS