Whale sharks are the animals that are most deserving of the name "gentle giants".
They grow to an incredible 18m (55 feet) in length and can reach an estimated weight of more than 42,000kg (100,000lbs).
They are known to travel great distances and they occupy all tropical and sub tropical oceans.
Yet very little is known about how they reproduce or why they congregate in the Galapagos Islands as they do.