Whale shark (Rhincodon typus). Whale sharks are the world's largest extant fish. They may be found in tropical waters worldwide. Whale sharks are filter feeders that extract plankton and small fish from seawater while swimming with their cavernous mouths wide open. Whale sharks average 10m in length and weigh an average of 20,000 pounds, but some individuals may reach twice that size. Photographed near Isla Mujeres, Mexico.