FLORIDA KEYS -- Aviva Diodato, a visitor from Arizona, was on a dive trip out of Islamorada two weeks ago when things went horribly wrong.

According to the Monroe County Sheriff's Office, Diodato asked for assistance during her group's first dive of the day and surfaced early. She made it safely to the stern of the dive boat and was removing her gear when she started to drift. By the time Diodato was located 15 to 20 minutes later, she was no longer breathing and her heart had stopped. Paramedics pronounced her dead upon reaching shore.

Diodato, who was 51, was the third diving fatality in the Florida Keys this year. And like her, the two other victims, Carol Strickland of Tallahassee and Thomas Pickett from Texas, were in their 50s.

In fact, Monroe County Medical Examiner's records dating back to September 2008, the time frame for which the office has reports logged on computer files, show that 10 of the 16 divers who perished were at least 50 years old. Both snorkelers who died during that period were also at least 50.

In addition, a Free Press review of articles and Sheriff's Office reports on Keys dive deaths for the eight months between November 2008 and the last days of 2007 show that four of eight divers who died were at least 50 as were both of the snorkelers who perished.

Some dive shop owners say the reason that many of the diving fatalities in the Keys occur among older clientele is simple demographics of who's putting on a scuba tank these days.

Middle-aged people are the ones who can afford the cost of a dive charter -- which can run up to $200 a day when factoring in equipment, said Connie Boykin, manager of Ocean Divers in Key Largo.

"You have to take in the factor of cost. Consensus with us is that [our customers] are in their 50s," she said.

But statistics show that the average diver is younger than that. A 2002 Keys diving survey conducted by Wegeningen University in Holland, and used by the Monroe County Tourist Development Council, placed the average age of divers at 33.

More broadly, a study published in late 2008 in the Diving and Hyperbaric Medicine journal found that in 2006 the average age of divers who purchased insurance from Divers Alert Network was 43.

Petar Denoble, M.D., research director for DAN, which is dedicated to the safety and health of recreational divers, says it is no mystery why most Keys dive fatalities in recent years are among those over 50.

"They are a bit less healthy than younger people," he said. "They are also a bit less physically fit than younger people."

Part of a trend

The Keys aren't alone in seeing more dive fatalities among the sport's older participants.

Denoble was among the authors of the 2008 study published in Diving and Hyperbaric Medicine in which researchers found that male divers who are older than 60 are four times more likely to die than male teenagers. Heart-related deaths were 13 times higher among divers over age 50 than those who are younger. The annual fatality rate for divers over 60 was 33 per 100,000 during the seven years of the study.

"We recommend that older divers adjust their participation in diving according to health status and physical fitness, maintain fitness with regular exercise and abstain from diving in conditions likely to require unaccustomed physical activity," the authors wrote.

James Loewenherz, M.D., medical director of the hyperbaric chamber at Mariners Hospital in Tavernier, said most diving deaths aren't the result of decompression, commonly called "the bends," but rather are caused by people inhaling too much water -- the same way snorkelers usually die.

In many cases those big gulps of water have as their origin minor heart abnormalities -- the heart skipping a beat, for example -- which force the diver to overexert, Loewenherz said. In other cases, people who have swelling -- more common as you get older -- are susceptible to having their lungs inundated with fluid once they are immersed, which also leads to overexertion.

Denoble says chronic, and frequently unknown, cardiac problems are often at the root of diving fatalities.

"They cause acute episodes that exacerbate underwater and divers drown," he said.

DAN suggests that all divers 35 and older have a physical examination annually.

Precautions

Aside from that, Denoble, Loewenherz and local dive shops say common sense is the best way for all divers, young and old, to stay safe. A physical exam is not required to achieve dive certification, though dive schools do screen people's medical history before enrolling them in a course.

On the other hand, if a certified diver books an excursion with a shop, no health screening is typically required.

"They're certified divers. They have a right to dive," said Brenda Mace, owner of Conch Republic Divers in Tavernier. "We cannot nor should the dive operator be responsible for the health of divers. It is an extreme sport."

Boykin, of Ocean Divers, said a few times through the years she has refused a customer due to their physical condition. But such a move is extremely rare, she added.

DAN organized a workshop earlier this month to discuss reducing diving fatalities. But the ideas circulated were all geared toward individuals, not businesses.

Boykin said many accidents in the Keys are preventable.

"The people who are having accidents are coming down here from a long winter up north, but they basically haven't done anything strenuous since winter onset," she said. "A 25-year-old can sit all winter and come out and dive, but a 50-year-old, they have to look after themselves."

rsilk@keysnews.com