These are the largest of the shark species. There are reports of whale sharks measuring 15 metres or more but the accepted reliable maximum was a specimen caught off Pakistan that measured over 12 metres and weighed over 20 tonnes (Gerald L. Wood, "Animal Facts and Feats", 1990).
In October 2006, an aerial reconnaissance survey revealed that there were over 70 whale sharks off the St Lucia area. By December they had moved as far south as Aliwal Shoal. This was excellent news as the numbers were apparently dropping off the South African coast during recent years. While whale sharks are protected in South Africa, they migrate over large areas and there was concern that they were being caught elsewhere. Anyway, they are back in full force.
Whale sharks are filter feeders and therefore harmless unless they hit you, by mistake, with their tails. This has happened to me when I drifted too close while filming and it was very painful.
On another occasion my dive team got even closer to a whale shark. A branch of Underwater Video Services specializes in commercial diving work. One day I received an emergency call from a nuclear power station on the west coast near Cape Town. A whale shark was stuck in one of the cooling water intakes. At first I suspected it to be a basking shark, another large filter feeding shark associated with cold water. It did, however, turn out to be a whale shark. I was unavailable so I sent a diving team to the power station. As the cooling water was essential for the running of the plant, the powerful pump, moving water at a rate of 20 cubic metres / second, was still running on arrival but was shut down for the rescue operation. The divers attached a rope to the shark's tail and pulled it to sea with the diving boat. Miraculously the animal survived and slowly swam off. Later I spoke with shark expert, Dr Leonard Compagno, about the incident. He explained that whale sharks are sometimes trapped in large eddies of warm water that travel southwards and around the Cape. Once the water temperature drops to the ambient temperature, the shark goes into a state of thermal shock, a normally fatal condition.