David Willis in Singapore: A monsoon whipped up waves which started flooding his boat

The 24-year-old actor was riding in a long tail boat - a traditional fishing canoe with an outboard motor - when it went down on Friday in heavy seas.

He was with British actress Tilda Swinton shooting his new film The Beach off Phi Phi Island in the Andaman Sea.

But despite newspaper reports to the contrary, 20th Century Fox co-ordinator Santa Pestanij - who was there when the boat capsized - said no sharks were seen near the boat.

"We did not underestimate the sea. There were at least four security boats present and prepared for the unpredictable," she said.

The accident cost tens of thousands of pounds in damage to camera equipment.

Helped calm nerves

Leonardo DiCaprio: "A real hero" after the boat went down

Santa added DiCaprio remained calm for the five to ten minutes he was in the water, and he helped calm the nerves of crew members who feared being drowned.

"He was a real gentleman, a hero," she said. said.

Divemaster Paul Davies, 27, of Llanelli, south Wales, told The Sun newspaper DiCaprio was "very cool".

Dive operators and tourism chiefs in the area have said some small sharks may swim in the area, but they had never heard of a shark attack.

Based on novel

The Beach has caused controversy in Thailand with local environmental activists suing Fox for allegedly damaging the eco-system of Maya Beach on Phi Phi Island.

Based on a novel by British author Alex Garland, it follows a young traveller - played by DiCaprio - who stumbles across a mysterious island inhabited by a group of backpackers. The book features a shark attack as part of the story.

DiCaprio, who is said to be earning £12m to play the role, said he would not tolerate any damage to Maya Bay. Fox vowed to return the beach to its natural state.

Around 100 mature coconut palms were planted on the beach and opponents say dunes were landscaped, ground cover was removed and coral was damaged.