A New Zealand tourist suffering chest pains while swimming has been rescued by volunteers on a Thai island.

Finlay John Hamill, 21, had taken a dip at a beach on Koh Rok island in Krabi province while his family rode a yacht on September 27.

However, the young man began to show symptoms of decompression sickness and had to be pulled back onboard. He complained of chest pains, prompting the family to call medics for assistance.

Rescue volunteers from the Mu Koh Lanta National Park rode a boat toward the yacht, where they found the stricken lad in pain but still conscious and able to walk.

They gave him first aid and then transported him to the Koh Lanta Hospital.

Neramit Songsaeng, head of the Mu Koh Lanta National Park, said: 'The national park received a notification that a yacht with a family of tourists onboard was asking for help because the son was suffering decompression sickness.

'The rescuers took a patrol boat and departed from Koh Lanta. It took three hours to transport the patient there because there were strong winds at the time, and Koh Rok island was very far.'