Phuket resident Sebastian Somesan, 46, had dived down to a depth of about 30 metres to free the snagged anchor of his speedboat.
Somesan, along with fellow Romanian Alexandru Florin Miron and Thai woman Saowalak Kanhawong, left Nai Harn Beach on his speedboat “Shonica” on Sunday.
His friends said they dropped anchor about 100 metres from the shore, but when they wanted to move on they found the anchor was stuck. They said Somesan decided to dive down to free it but failed to surface after the anchor was released.
Miron and Saowalak said they searched for the missing man before calling emergency services.
A search and rescue mission was launched immediately, coordinated by Rawai Mayor Aroon Solos, the Third Naval Area Command, marine police and Kusoldham Phuket Foundation.
Meanwhile a command centre has been set up at Ya Nui Beach as a contact point for the missing man’s friends and relatives.
On Wednesday, Aroon said 35 personnel boarded a speedboat, rubber dinghy and jet skis to search for Somesan around the two islands of Koh Kaew Nok and Koh Racha Yai.
Officials have also searched coastal waters from Nai Harn Beach in Rawai to a cape in Patong. Meanwhile, a team of divers searching the waters of Koh Kaew Nok has found no signs of the missing man.
Phuket Governor Narong Woonciew said that strong currents are hampering search efforts.
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