WET weather that triggered floods across southern Thailand has helped to give Phuket and Andaman coast reefs a good chance of recovery from extensive coral bleaching.

The dousing in March and more grey clouds this week have reversed the situation of 2010, when blue skies and hot sun through April and May exposed reefs to extensive damage.

Today, says Dr Nalinee Thongtham of the Phuket Marine Biological Centre, young coral can be seen blooming at reef sites around the region.

''It's an excellent sign,'' she said. ''We think the reefs stand a chance, although they need a lot more time yet.''

The clouds, though, are not all silver lined. Run-off from construction sites during the unexpected downpours of March has covered some coastal Phuket corals with silt, Dr Nalinee said.

This was even more deadly than the bleaching. She said one resort, Le Meridien Phuket at Relax Bay, south of Patong, had called in marine biologists to check the condition of nearby reefs.

The reefs near the resort were healthy and showing signs of regrowth, despite a greater quantity of earth washing down a bay canal from hillside construction sites, she said.

A check on other reefs in the region also showed hopeful signs, she said. Similans Marine Park ranger Mana Permpoon confirmed that reefs in the park, closed now until November, were showing signs of regrowth.

Several popular dive sites throughout the region were shut down by officials after the full effects of last year's coral bleaching became evident. The sites are mostly in shallower waters, where the suns rays have been able to penetrate more easily.

Deeper sites remain unaffected. It's expected to take at least five years for the corals to fully recover. About 70 percent has suffered from bleaching.