Tens of thousands of tourists from around the world visit Thailand's famous dive sites each year. But marine experts say the killer tsunami two weeks ago has temporarily damaged some of the area's picture perfect coral reefs.

Scuba divers have been scouring the depths of the Andaman Sea, in some of Thailand's favorite dive spots. They are clearing away debris littering the seabed - all carried by the killer tsunami two weeks ago.

Charoen Nitithamyong, a marine biologist at Thailand's Chulalongkorn University, explains how debris - such as furniture and vehicles - dragged off land by the giant waves caused the damage.

"Coral is an animal but they have algae living inside the coral and those algae need the light to photosynthesize," he explained. "So when the corals are covered by these things the coral couldn't survive."

The Thai government says its initial assessment shows overall about five percent of coral reefs have been harmed. The damage is most extensive around South Patong Beach - with 20 percent devastation - and Koh Pai and Rana Bay off Phi Phi Island, which lost almost half the reef.

Ukkrit Satatoomin, of the Phuket Marine Biological Center, says the situation is not that bad given the catastrophe.

"I think the effect of the tsunami to coral is very minor. The damage is restricted only to specific sites in Phuket," he said. "But the major reef areas are still in good condition, some places have been untouched by the tsunami."

The United Nations has sent some equipment to help divers clean up the Andaman Sea. Mr. Ukkrit is optimistic.

"Coral can heal itself. Even the coral that get damaged like breaking off or even turned over, some parts of it is still alive. I'm sure within three or five years that we can see the coral in good condition again," he said.

Elsewhere in Asia, Indian marine experts are also examining marine life off the coast of Kerala, which was also hit by the tsunami. It is feared that the killer waves may have killed or displaced rare sea turtles in the Indian Ocean.