Whale sharks are filter feeders, which means that they eat massive amounts of tiny crustaceans, plankton and other small organisms. They have specialized passive filter structures in their mouths that allow sea water to pass through and strain out food matter.
Filter feeding is the same method of feeding used by clams, krill, sponges, jellyfish, manta rays, whales and several other species of sharks. Additionally, many species of bottom feeder or foraging fish are filter feeders and play an important role in regulating the ocean's food chain and water quality. The Atlantic menhaden is a type of herring that filters four gallons of water per minute, removing massive amounts of plankton from the ocean's water daily.