The Gentle Giants of Donsol "Butanding!" our spotter screamed. "Get ready", our Filipino guide advised. At his prompt — "Go, go, go!" — everyone leapt into the water and swam towards the dark, approaching shape. Soon we were close enough to see that the giant form was a whale shark or "butanding". This plankton-eating shark, Rhincodon typus, is found in the world’s tropical seas. The largest specimens are 15m (50ft) long, making them the biggest fish in the world. The migratory whale shark feeds largely on plankton, as well as on small fish and crustaceans. It is the only large shark with its mouth at the front of its head rather than underneath, but the creature is docile and harmless to humans. The Marine Conservation Group presents a multimedia talk by Stephen Lau, Victor Tan and Dominique Low, who will share their unforgettable interactions with whale sharks encountered at Donsol, the Philippines, at 7.30pm at the NSS Office.