A 30-year-old Hong Kong man died on a diving trip in Okinawa, Japan.
The Hong Kong tourist joined a diving experience tour in Cape Maeda, which is the best spot in Okinawa as it is famous for its "blue cave."
According to reports, the man started the dive an hour before the accident.
When he was swimming with his wife and other participants on the coast of Onna Village in Cape Maeda at around 5pm on Sunday, he felt unwell and shouted for help. Other swimmers immediately alerted tour staff, who called the police and rescue team.
The owner of a diving shop in Cape Maeda said his employees heard the man yelling and went to his assistance.
At the time, the man wore diving equipment, and his Japanese diving coach was next to him.
His eyes were blood-shot, and he was in a semi-conscious state when he was brought ashore.
Japanese authorities said his heart and lungs were not functioning when he was pulled out of the water. An automated external defibrillator was used on him.
He was sent to hospital while unconscious and certified dead upon arrival.
Officers of the Japan Coast Guard from its headquarters in Naha are investigating the cause of death.
Hong Kong's Immigration Department has contacted the Office of the Commissioner of the Ministry of Foreign Affairs in Hong Kong and the Chinese Consulate-General in Fukuoka to gain a better understanding of the situation.
It contacted the man's family to provide advice and assistance, a department spokesman said.
Surrounded by big reef rocks, Cape Meade is known for its crystal clear waters and colorful tropical fish. The location is also suitable for beginner divers.
The Blue Cove in particular is a popular diving spot, as the water appears to be in an azure blue color as sun shines into the seaward limestone cave.
Diving instructor Oliver Ng Yau-cheong, who has 29 years of experience in scuba diving, said a swimming test is not required for non-divers to go scuba diving and they can join a beginner's exploration tour.
"Participants are required to fill in a questionnaire to declare their health condition. Diving coaches will check the questionnaire before allowing them to dive but they are not responsible for verifying clients' health records," he said.
In most places, a diving coach will guide and lead two to three clients, he said.
Ng warned people not to do any vigorous exercises after diving, as they may suffer or even die from decompression illnesses, symptoms include headaches, extreme fatigue, numbness and skin rashes.
The general recommendation is to avoid strenuous exercise for 24 hours after diving, he added.
Decompression illness occurs when a diver ascends too fast. It may also occur when a person does vigorous exercise after diving, because the air bubbles in the joint, lungs and blood vessels will disrupt normal blood circulation.
