According to the Phuket Gazette, the 30m-long Choke Somboon 19, run by Dive Asia, was hit by a tornado which came out of nowhere in otherwise calm conditions.
The boat's skipper, Chakri Leechuay, reported that the boat was hit by a vortex of "red wind" at 11pm on Sunday night, while on passage about 13 miles from Patong Beach.
The tornado appeared on the radar while still three nautical miles away, yet arrived within ten minutes. The boat was spun violently, heeled, filled and sank.
Leechauy was, however, able to get out a distress call. Twenty-three survivors were picked up from liferafts about three hours after the sinking, by fishing boats and marine police.
The missing have been named as German Jetzinger Gabrielle, Japanese Yuba Hirotsuga, Austrians Klaus Konradder and Monika Schuster, Swiss Sibylle Bucher and Rolf Niederberge, and Thai Jumpa Sorntat, the boat's cook.
The rest of the boat's crew and diving staff were reported to be among those who were saved.
Leechuay told journalists that he knew bad weather might arise, but had judged that the boat, a modern design just six months old, was seaworthy enough to cope with heavy weather. The tornado was an unexpectedly freak occurrence, he said, such as he had never experienced in 20 years afloat.
A Royal Thai Navy boat and helicopter are continuing a search for survivors or bodies.
An employee of the Phuket-based Dive Asia has reportedly told police that the company's insurance policy provides for 200,000 baht per passenger, either for medical expenses or in the event of death.
Archive | 
Win a Luxfer pony cylinder
