Unexplained Snorkel Deaths in Hawaii

For years, snorkeling in Hawaii has been the leading cause of tourist deaths. Snorkel-related drownings with no signs of distress have often been a mystery. A new study by the Hawaii State Department of Health offers some reasons.

According to the project director, Carol Wilcox, the study refutes the belief that snorkeling-related deaths are just from water inhalation. She said most snorkel-related fatal and near-fatal drownings are due to low levels of oxygen in body tissues prompted by excess fluid buildup in the lungs, otherwise known as hypoxia induced by rapid onset pulmonary edema, or ROPE. [Undercurrent has been writing about this problem in scuba divers, referring to it as swimming-induced pulmonary edema (SIPE).]

The study also connects snorkel-related drownings with a cardiac condition that restricts the heart's ability to fill with blood between beats. Wilcox said this cardiac condition helps explain why middle-aged men are more likely to be affected.

Snorkel Resistance

Another predisposing risk factor the study discovered is breathing through a snorkel with too much resistance. This causes an increase in negative pressure in the lungs and can also result in SIPE.

The study says SIPE accounts for the lack of distress signals in many snorkel drownings as it causes muscle fatigue and loss of consciousness and can also be triggered by a heart condition.

By contrast, when drowning due to the inhalation of water, there are often obvious signs of struggle.

The main difference is the source of the excess fluid. In SIPE, the excess fluid is not inhaled into the windpipe. Instead, a buildup of bodily fluids seeps into the lungs, reducing the ability to deliver oxygen to the body, leading to a lack of sufficient oxygen.

Hawaiian Deaths

There were 204 snorkeling-related deaths in Hawaii from 2012 to 2021. Of those, 184 were tourists. John Titchen, the chief of the Honolulu Ocean Safety and Lifeguard Services, says one reason that tourists die from snorkeling is their unfamiliarity with Hawaiian waters and with snorkeling in general. "The waters are tranquil and crystal clear, and they think it looks easy," Titchen said.

The study's authors surveyed people who had survived near-fatal drownings . Wilcox said 71 percent of the 131 survey participants reported calm conditions, 87 percent reported good visibility, 63 percent reported at least sufficient snorkeling experience, and 88 percent reported at least sufficient swimming ability.

Almost two decades ago, she went for a swim with her fins and a new snorkel mask in Waikiki and swam out and suddenly became short of breath and lost strength in her arms. "I started to hear this huge heartbeat in my ears, like deep drums ... I knew I was going to die," Wilcox said, adding that she survived because she was pulled out of the water and given oxygen.

Not only was Wilcox using an unfamiliar snorkel, which may have contributed to her near-fatal drowning, but the incident occurred a day after she returned to Hawaii from Canada, a flight time of around seven hours.

Long Flights a Potential Cause

The Snorkel Safety Study is the first to hypothesize that long-haul air travel may be a significant predisposing factor to snorkel-induced SIPE, which could also help explain why so many snorkeling-related fatalities are tourists. Most incoming visitors have spent a minimum of five hours on an airplane at a cabin pressure up to 8,500 feet elevation.

Dr. Philip Foti, a Kailua pulmonologist and the study's principal investigator, said there have been few studies "to determine both the effects of high altitude on those with certain types of lung disorders, as well as in those without any."

Jumping from a boat

Besides identifying plane travel as a possible predisposing risk factor, the study is also the first to identify the added risk of snorkeling from a boat. "It takes a lot of effort to jump into water where you cannot touch bottom," Wilcox said. "Adjusting your mask and snorkel and fins, and then swimming away ... chances of survival are better if the incident happens where the snorkeler can touch bottom."

High Resistance Snorkels

The study was unable to conclude the risk of using a full-face snorkel mask, as only four of the 50 masks the study group tested were full-face masks.

"The safest option is to use a mask and snorkel that doesn't have various modifications of the tip to keep water from entering. Use a straight snorkel and mouthpiece that are both adequately sized, and make sure there are no faulty or narrow valves," Foti said.

- Reprinted from the Honolulu Civil Beat and written by Alicia Lou