I copy it from Wikipedia.
The whale shark, Rhincodon typus, is a slow filter feeding shark that is the largest living fish species. It can grow up to 12.2 m. in length and can weigh up to 13.6 tonnes (15 short tons). This distinctively-marked shark is the only member of its genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before 1984), which is grouped into the subclass Elasmobranchii in the class Chondrichthyes.
The shark is found in tropical and warm oceans and lives in the open sea and can live for about 70 years. The species is believed to have originated about 60 million years ago. The name "whale shark" comes from the fish's physiology; that is, a shark as large as a whale that shares a similar filter feeder eating mode. The whale shark inhabits the world's tropical and warm-temperate oceans. Though it is often seen offshore, it has also been found closer to shore, entering lagoons or coral atolls, and near the mouths of estuaries and rivers. It's range is generally restricted to about ±30 ° latitude. It is capable of diving to depths of over 700 metres. The whale shark is not an efficient swimmer since the entire body is used for swimming, which is unusual for fish and contributes to an average speed of only around 5kilometre-per-hour. The whale shark is a filter feeder — one of only three known filter feeding shark species. It feeds on phytoplankton, macro-algae, plankton, krill and small nektonic life, such as small squid or vertebrates.
This species, despite its enormous size, does not pose any significant danger to humans. It is a frequently cited example when educating the public about the popular misconceptions of all sharks as "man-eaters". They are actually quite gentle and can be playful with divers. There are unconfirmed reports of sharks lying still, upside down on the surface to allow divers to scrape parasites and other organisms from their bellies. Divers and snorkelers can swim with this giant fish without any risk apart from unintentionally being struck by the shark's large tail fin.
The whale shark is targeted by and commercial fisheries in several areas where they seasonally aggregate. The population is unknown and the species is considered vulnerable by the IUCN.