The whale shark (Rhincodon typus) is a slow-moving filter-feeding carpet shark and the largest known extant fish species. The whale shark is found in open waters of the tropical oceans and is rarely found in water below 22 °C (72 °F). Modeling suggests a lifespan of about 70 years, but measurements have proven difficult. They have very large mouths and are filter feeders, which is a feeding mode that occurs in only two other sharks, the megamouth shark and the basking shark. They feed almost exclusively on plankton and, therefore, are completely harmless to humans.