Mysterious Snorkel Drownings Explained, Snorkel Safety Study (Interim Report)
Authors: Carol Wilcox, Philip R. Foti, Ralph S. Goto
DOI / Source: n/a
Date: 01 July 2020
Reading level: Beginner
Why This Matters for Freedivers
A lot of freedivers and spearos spend long periods on the surface breathing through a snorkel, often after travel and sometimes with heavy exertion (swimming against current, towing a float, fighting chop). This report argues that some “quiet” snorkel drownings may start as sudden lung fluid build-up (ROPE), not panic or lack of skill. The big takeaway is practical: breathing resistance + hard exertion + certain health risks can create a dangerous hypoxia spiral with few obvious distress signs.
Synopsis
Snorkeling is often treated as the “easy, safe” water activity. Yet Hawaiʻi has seen a troubling pattern: people found motionless near shore, in calm conditions, sometimes soon after entering the water, with little or no visible struggle. This interim report was produced to investigate what might be driving these mysterious cases and what risk factors could be involved.
The report’s central claim is that many of these incidents may be explained by Rapid Onset Pulmonary Edema (ROPE)—a fast build-up of fluid in the lungs that blocks oxygen transfer to the blood. The mechanism described is straightforward: when you inhale through a narrow tube (a snorkel), especially while lying prone at the surface, you may need to generate stronger negative pressure in the chest to pull air in. If that “suction” pressure is strong enough and persists, it can draw fluid from lung capillaries into the air spaces. Once fluid begins to accumulate, breathing feels harder, the person often breathes faster, resistance rises even more, and oxygen levels can crash quickly. The report stresses that this pathway can look “quiet” from the outside—more like sudden weakness, confusion, and collapse than a dramatic struggle.
A major part of the project tested real-world snorkels using a device created for the study (SARA), showing that airflow resistance varies widely across snorkel designs. Importantly, you can’t reliably judge resistance just by looking. The report also notes that resistance rises with increased airflow—meaning the harder you work, the harder it can become to breathe through some snorkels. Full-face masks did not show an inherent resistance advantage or disadvantage overall, but the report highlights practical concerns: they can be harder to remove quickly, you can’t simply spit out a mouthpiece, and certain malfunctions may increase aspiration risk.
Beyond equipment, the report points to health factors that may increase vulnerability (especially certain cardiac issues linked with elevated filling pressures) and explores the hypothesis that recent long air travel could be a contributor for visitors, potentially affecting lung susceptibility. It also reports survey and case-study findings suggesting ROPE-like symptoms are common among people who “got into trouble” while snorkeling.
The overall message is prevention-focused: snorkeling is not automatically benign, distress may be minimal or absent in ROPE-type events, and safer choices (lower-resistance snorkels, avoiding overexertion, buddy systems, and medical caution when appropriate) may reduce risk.
Abstract
This interim report summarizes a Hawaiʻi snorkel safety investigation aimed at identifying causes and risk factors for fatal and non-fatal snorkel incidents. The study proposes that many cases may involve hypoxia triggered by Rapid Onset Pulmonary Edema (ROPE), a process in which negative pressure during inhalation contributes to fluid accumulation in the lungs, causing rapid oxygen failure with few outward signs of struggle. Testing of snorkels showed wide variability in inhalation resistance, increasing with exertion and not reliably predictable by appearance. The report also discusses potential contributing factors including certain cardiac conditions and recent prolonged air travel, evaluates survey and case-study findings, and provides practical safety messages for snorkelers.