The Jogasaki Coast in Ito, Shizuoka Prefecture, is one of the most popular scuba diving spots in the country. Medical emergencies are emerging as a major cause of accidents. (Kazuhiro Ichikawa and Kensuke Yamazaki)

Photo/Illutration Scuba divers prepare to dive at the Jogasaki Coast of Ito, Shizuoka Prefecture, on June 6. (Keisuke Yamazaki)

ITO, Shizuoka Prefecture—The rocky Jogasaki Coast here is one of the most popular scuba sites in Kanto.

It’s where crystal clear Pacific water surges along the volcanic coastline, with no river deltas to muddy the visibility. Divers are drawn to the rich biodiversity, including giant squid and clownfish.

What they don’t count on is the exertion required of the human body.

Twelve divers died or disappeared during scuba expeditions off the Izu Peninsula between 2013 and 2022, according to Japan Coast Guard figures. Four were off the Jogasaki Coast, five off Cape Osezaki in Numazu and three off Yawatano beach in Ito.

Ten of the 12 were aged 40 or older. Five died from heart failure, brain disease or unspecified poor health on the day of the dive. The cause of death of the others was unattributed.

Experts say middle-aged and older individuals with health issues should think twice before booking a dive because they are more prone to problems underwater.

The nonprofit Shizuoka Prefecture Divers Conference has identified the problem and is working to reduce the number of accidents. At its heart is the new prominence of health issues, given that equipment failure has become less common.

“Compared with before, divers today are better informed about how to avoid accidents. Diving equipment has been improved and is less likely to malfunction,” said Toru Wagatsuma, head of the group’s secretariat.

Scuba diving is a sport that people can enjoy throughout their life. There are even divers in their 80s, according to local dive shops.

But it does not mean that the sport is safe for all. The deeper you dive, the greater the water pressure. And it is not surprising that some divers experience mental stress when the scuba air supply is their only source of oxygen.

In such conditions, individuals are more likely to experience a medical emergency.

Coast Guard records show that nationwide 135 divers died or disappeared and were presumed dead over the decade from 2013. The figure is smaller than the 979 deaths during fishing and 626 people who died during swimming.

Still, it is notable that many of the victims were in their 50s.

It is routine for many dive shops to ask clients how they feel the day before the dive. In particular, they sometimes ask people aged 45 or above about their blood pressure and cholesterol levels.

There is no way for the instructors to verify the answers.

“There was one case where an individual had high blood pressure and was taking medicine for it, but did not tell the instructors,” Wagatsuma said.

If someone has a heart attack at Futo Port in Ito, there is an automated external defibrillator nearby. Such a device can stimulate a stopped heart to resume beating.

Diving instructors in the area receive emergency response training annually, in coordination with the Coast Guard and firefighters.

Takuya Yakita, head of Ito-based dive shop Jogasaki Indies, urges senior divers with health issues to think of the risk if they become ill mid-dive.

“We are not saying that they should refrain from diving, but we encourage them to take extra safety precautions,” Yakita said.

He added that in the future, a doctor’s report may be required from older divers.

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