Thai rescuers pulled 21 bodies from waters off the coast of the holiday island of Phuket on Friday after a tourist boat went down in heavy seas with dozens of Chinese passengers on board.

The dead were found drifting face down in the water, still wearing life jackets, several miles from where the Phoenix sank after being hit by five-metre (15-foot) high waves in a storm on Thursday evening.

Divers reported seeing "over 10 bodies" floating inside the hull of the submerged boat, according to Thai navy Rear Admiral Charoenphon Khumrasee, who said they would try to retrieve them later Friday.

One survivor, a Chinese woman, was rushed to hospital in Phuket, according to a reporter at the scene, after she was found several miles from the boat, floating near the bodies of fellow passengers. Her condition was unknown.

The boat was carrying 105 passengers, mostly Chinese tourists, when it sank.