A British tourist has been found dead after his air supply ran out while diving 398ft underwater in Thailand.

Roger Matthew Smith, 60, and his Thai friend Torsak Varinchaikamol, 56, were exploring an idyllic diving spot in Nakhon Si Thammarat, southern Thailand on Saturday afternoon.

Both dived with air supplies that could last an hour, with the Brit going down to 398ft while his partner dived to 360ft deep in the vast lake.

A British tourist has been found dead after his air supply ran out while diving 398ft underwater in Thailand

After 47 minutes the Thai diver returned to the surface and saw his friend sprawled on rocks on the shore.

He thought he was resting but when he went to talk to the Brit but found that he had already stopped breathing. Torsak immediately contacted emergency services for help.

The victim was taken to hospital where medics tried to revive him, but he was pronounced dead.

Police investigators said they asked diving specialist Porasu Gomaratat, 44, to examine the case, who said he is likely to have died from a sudden change in pressure or asphyxiation.

He thought he was resting but when he went to talk to the Brit but found that he had already stopped breathing. Torsak immediately contacted emergency services for help

Diving equipment at the scene. He is believed to have tried to desperately float back to the surface after seeing his oxygen supply running down

He is believed to have tried to desperately float back to the surface after seeing his oxygen supply running down.

He said: 'The data from the victim's diving watch shows he rose from the deep water to the surface swiftly while his oxygen supply was running out and his helium tank was not working well.

'The helium tank is to help reduce the intoxication of nitrogen and oxygen when diving deep and its malfunction could cause asphyxiation.

Diving equipment from the scene. Police investigators said they asked diving specialist Porasu Gomaratat, 44, to examine the case, who said the victim is likely to have died from a sudden change in pressure or asphyxiation

People gather at the edge of the lake where a 60-year-old British man died on Saturday

'Moreover, rising from the deep water to the surface quickly can caused a pressure change that prevents enough oxygen to travel to the brain, which can cause a shock to diver.'

Police Colonel Chokdee Rakwattanapong said they will take the body to the province hospital for the post-mortem examination.

He said: 'The body was delivered to the hospital and we will wait for the examination result before we could confirm the cause of his death.'