Bangkok  - Frogmen on Thursday retrieved the bodies of five foreigners from a boat that sank in a sudden storm over the weekend after a diving tour to Thailand's Similan Islands in the Andaman Sea.

"We found the bodies of three foreign men and two women who had been trapped inside the boat when it sank," Marine Police Lieutenant Colonel Wanlop Phuangbaka said.

On Tuesday, authorities found the body of a Caucasian woman floating near the area where the boat sank Sunday. One Thai national, a member of the dive boat's staff, was still missing.

The 29-metre Choke Somboon 19 scuba-diving-boat-cum-floating-hotel sank late Sunday in 70 metres of water after being hit by a sudden tornado, the crew and survivors said.

The dead foreigners were three Austrians, two Swiss and a Japanese national.

The corpses were sent to a hospital on the island of Phuket for identification, Wanlop said.

Twenty-three passengers, including 15 foreigners and eight Thai staff, made it to life rafts and were rescued by a Thai fishing boat Monday morning.

Most of the passengers were in the boat's saloon deck when the twister hit about 30 kilometres off Phuket, a popular Thai beach resort about 600 kilometres south of Bangkok.

The boat itself is advertised on the company's website as its "luxurious flagship," with air-conditioning, a saloon, a multimedia centre and a large sun deck.

A typical tour takes scuba divers to the Similan Islands from Phuket, allowing them to dive all day and then sleep on the boat as it sails back to Phuket overnight, which takes 10 to 12 hours.

The Similan Islands, a national marine park, is one of Thailand's best-preserved scuba and snorkeling destinations. Hotels and guesthouses are prohibited on the islands to conserve the environment. (dpa)