The smallest ever recorded was about 15 inches (38 cm) long, but there are reports of them over 20 m (62 feet) long although there is some lack of evidence concerning ones this big.
There have certainly been accurate records of this fish 12 m (37 feet) long.
The Whale Shark species is possibly as much as 60 million years old, but has only been known to western science since about 1828.
Individuals may live for as much as 100 years, but as with many things about the interesting species there is some guess work concerning their life span.
It is listed as migratory and vulnerable, but again this is partly based on how little we really know about them.
The Whale Shark is a plankton feeder and filters large quantities of seawater, removing plankton of above about 2 cm and swallowing it.
In addition, much of the smaller plankton is also captured by a settling process in the shark's mouth.
They will actively seek out concentrations of plankton, and their appearance at some locations off the coast of Western Australia, including Ningaloo Reef each year between April and July, coincides with mass spawning of coral.
They are live bearing fish like the Guppy although the Whale Shark is bigger than the Guppy.
Little is really known about their breeding.
They seem to prefer warmer water between 30 degrees north and 35 degrees south.
It is probable that most of the their feeding is on or near the surface because this is the main place they are likely to find high concentrations of plankton, but they can certainly dive as deep as 700m (2200 feet).
One of the most reliable places to find Whale Sharks is off the coast of Western Australia.
Whale Sharks have been kept in large aquariums for public display and study, but this is not a fish I recommend for home aquariums.
It is a peaceful fish, not attacking Humans or other big things.
Humans can swim with them, but care needs to be taken to avoid their tail as they swim.
They do not appear to be efficient swimmers, but still seem to cover long distances.