Whale sharks (Rhiticodon typus) are not whales and they are not mammals. They are the largest fish in the world. An average whale shark is around 25 feet long, but they can reach up to 40 feet long. As with most sharks, the females are larger than the males.

You would think that with such a massive body this shark would be a fierce predator, but this mammoth fish is quite mild-mannered. It likes its solitude. Its mouth, which looks quite threatening, can open up to four feet wide and has about 310 rows of teeth, or about 3 000 teeth in all. The interesting thing is, this gentle giant doesn't even really use the teeth. Instead, it filters plankton and krill through its gills for nourishment by simply opening its enormous mouth to take in a large amount of water. The plankton stay in the mouth for nourishment while the water strains through gills in the side of the mouth. Even though a whale shark has a huge body, its gullet is relatively small. So while a whale shark could fit larger food into its mouth, it would not be able to swallow it.

Whale sharks are quite beautiful. Their back and sides are a reddish or greenish-brown. The top of the body has white or yellowish spots and stripes of varying sizes, and the underside is whitish or yellowish-white. A diver looking for such beauty has nothing to fear: Whale sharks are harmless to people, and if met by a diver, would probably ignore him completely. They live in the open seas all over the world, preferring to stay in areas close to the equator for the mild temperatures. They reach adulthood at 25 to 30 years of age, and they may live to be 100 years old.