Snorkeling causes more ocean drowning deaths among visitors in Hawaiʻi than any other activity, and the study the state tourism authority funded concluded that the snorkel itself is part of the problem. Many of these deaths happen in calm water, often shortly after the person enters, and usually with no visible sign of distress. Here is what the state's own numbers say, and where on Hawaiʻi Island people run into trouble.
Between 2014 and 2023, snorkeling accounted for 225 ocean drowning deaths in Hawaiʻi, more than any other activity. Swimming came in at 188. Of those 225 snorkeling deaths, 205 were visitors. Over the 2019 to 2023 window the Department of Health puts the visitor share of snorkeling victims at 91 percent, while visitors comprise about 12 percent of the state's de facto population.
Visitors have eight times the drowning fatality rate of residents. Drowning is the leading cause of fatal injuries among visitors in Hawaiʻi; among residents it is the fifth leading cause.
For this island specifically: Hawaiʻi Island recorded 114 fatal ocean drownings between 2013 and 2022, an average of 11 a year, with 54 percent of the victims visitors. Over 2019 to 2023, Hawaiʻi County's ocean drowning rate was 24.3 per 100,000, lower than Kauaʻi (49.1) and Maui (45.7) but above Honolulu County (17.7).
The Hawaiʻi Department of Health formed a Snorkel Safety Sub-Committee in October 2017 in response to frequent snorkel-related drownings, particularly among non-residents. Many of the incidents were puzzling: they often occurred in calm water, sometimes shortly after the person entered, and typically without any visible signs of distress. In January 2019 the Hawaiʻi Tourism Authority funded the resulting Snorkel Safety Study, led by Ralph Goto, pulmonologist Philip R. Foti, M.D., and Carol Wilcox.
Taken together, the study's findings showed that the problem is the snorkel. Breathing through a narrow tube creates resistance during inhalation, which lowers lung pressure and draws fluid from surrounding capillaries into the air spaces. Each subsequent inhalation draws in more, progressively cutting oxygen intake into the blood, and the snorkeler becomes short of breath. That oxygen shortage, hypoxia, leads to loss of muscle strength and confusion, then loss of consciousness and clinical death, sometimes within minutes of the first signs. The study named it Snorkel-Induced Rapid-Onset Pulmonary Edema, or SIROPE, and identifies it as a relative of the pulmonary edema already documented in scuba divers, long-distance swimmers, and mountain climbers.
The practical difference from a classic aspiration drowning is the apparent absence of a struggle. The study's own headline is worth repeating: snorkeling itself is a hazard, and recreational snorkeling is not a benign, low-risk activity, for experienced and inexperienced swimmers alike.
If you unexpectedly become short of breath, do not push on and do not try to power back to shore with the snorkel still in your mouth. The study is explicit that exertion while trying to reach shore or escape a current while continuing to breathe through a snorkel worsens the situation.
Remove your mask and snorkel. Get on your back. Signal for help. Then get to shore or to a boat the best way possible. Loss of strength and confusion are part of the same hypoxia sequence, and none of it is a reason to finish the swim first.
Dr. Foti built the Snorkel Airway Resistance Analyzer to measure inhalation resistance, and tested 49 snorkels: 16 simple ones, 29 with wet/dry mechanisms, and four full-face masks, each at three airflow levels. Resistance varied widely. Simpler snorkels generally had lower resistance, but because a tube can narrow internally, a visual assessment of the narrowest opening does not tell you which snorkels have the least resistance.
Full-face masks offered no inherent advantage or disadvantage on inhalation resistance. Their problems are mechanical: difficulty in urgent removal, inability to spit out the mouthpiece, trouble clearing water with a sharp breath, and they are unsafe for diving beneath the surface. Valve malfunction can lead to serious aspiration risk. The theory that carbon dioxide accumulating in the mask knocks snorkelers unconscious was examined and found not to be a physiologically viable explanation.
Then there is the flight. On long-distance flights the cabin is pressurized to simulate conditions between 8,500 and 9,500 feet, and passengers to Hawaiʻi often experience that for five to nine hours or more. Extended time in that environment can weaken lung walls and cause edema, often noticeable as swollen ankles, and it is more common in older individuals and those with heart issues. Lungs usually recover after a few days at sea level, which is why the study recommends considering a 2 to 3 day wait after extended air travel before snorkeling.
Dr. Foti examined Coroner's Office records from 2018 and 2019 to see whether autopsies could differentiate drowning by aspiration from drowning by SIROPE. They could not: both involved liquid-filled lungs and death by hypoxia. What the autopsies did reveal was pre-existing health conditions and a correlation between drownings and cardiac disease, especially elevated Left Ventricular End-Diastolic Pressure in older individuals. Drugs and alcohol were rarely factors.
The separate case studies investigation, in which Dr. Foti interviewed survey participants and reviewed their medical records, identified elevated LVEDP as a risk factor for SIROPE. The study's safety tip for anyone with a heart condition is one line: consider not snorkeling.
Kahaluʻu Beach Park takes nearly half a million visitors a year. It has lifeguards, but only from 9:30 a.m. to 4:30 p.m., and the Kohala Center strongly recommends waiting until they are on duty before entering the water. Conditions in the bay can change rapidly, and large waves, strong currents, sharp rocks, sea urchins, and other hazards are common. Use the channel in front of the lifeguard tower to enter and exit rather than picking your way over the rocks.
Hōnaunau Bay, the Two Step, has no lifeguard in our data. The entry is a lava shelf that the Park Service describes as uneven, loose, and sometimes wet and slippery, and the area is primarily a boat ramp, so you are sharing it with boat traffic. The Park Service warning for this coast is to never turn your back on the ocean, because large waves can appear with little or no warning. Check for high surf and high wind warnings before you leave.
The state's 2025 Hawaiʻi Water Safety Plan maps Hawaiʻi Island's drowning black spots by name. Several are places visitors go for the snorkeling or the photo:
Lifeguards do not make a beach safe either. Hāpuna is guarded and State Parks still posts a warning about dangerous rip currents and pounding shore breaks during periods of high surf, with the plain instruction that waves over 3 feet high are for experts and all others should stay out of the water and away from the shoreline.
Ocean Safety on Hawaiʻi Island is administered by the Hawaiʻi Fire Department, with two Ocean Safety Captains overseeing Hilo and Kona. The 2025 state plan is candid that a small tax base funds ocean safety patrols for a large area of mostly remote coastlines, saturated by the same visitor loads as other counties. Of the 28 Hawaiʻi Island beaches OceanSafe tracks, 11 have lifeguards: nine year-round and two seasonal. Most of the coast has none.
The Snorkel Safety Study's own ten safety tips:
Check live conditions for the specific beach on the specific morning, and if you are going out mainly to see honu, read the sea turtle guide first so you know the distance rule before you are in the water with one.