The boat, named ‘Martini’, sank near Nam Bo Bay on the west side of Koh Hei at about 3:50pm.
The boat departed from Chalong Bay Marina pier at 9:40am, with planned stops including Koh Maithon and the Racha islands, reported Phuket Marine Chief Natchapong Pranit.
The sinking occurred while the boat owner and operator, Chakri Kaenkhong, 31, was mooring at Nam Bo Koh Hei Bay, Mr Pranit said.
On board at the time were nine people: six Russians, including four boys aged 4, 9 and 14 years old; along with Mr Chakri and his crew, Amarin Danadee, 17, and Phattharapon Kothalin, 44.
Mr Chakri explained that the primary cause of the sinking was water entering the engine room due to a leaking water pipe. Despite the crew’s efforts, the water entered too quickly for the crew to pump out in time, leading to the boat sinking, he said.
Fortunately, at the time of the incident, the weather was normal, and wind and waves were calm, he said.
The nearby vessel ‘Panwa Princess’ rendered assistance in rescuing all tourists and the boat crew. The rescued individuals were safely delivered to the pier of Cape Panwa Hotel in Wichit, where they received assistance.
All passengers and crew members emerged unharmed from the incident, and there was no oil leak detected in the area where the boat sank, Phuket Marine Chief Mr Natchapong said.
The tourists were later taken to the hotels in Karon, where they were staying, he added.
The boat registration had not expired, and the ship operator’s certificate was still valid, Mr Natchapong confirmed.
However, the vessel lacked an engine operator or engine operator license.
The boat was also found to be used for the wrong purpose, violating conditions outlined in the boat license, he added.
The Phuket Marine Office will “take legal action to the fullest extent concerning these violations”, Mr Natchapong said.
Lighted buoys marking the sunken boat’s location are to be installed until the wreck has been salvaged, he added.
Authorities assure the public that updates on the progress of the investigation will be reported promptly as the situation unfolds, said an official report of the incident.