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Preventing Drowning From Underwater Breath-Holding

Alyssa Keehan, Esq., CPCU, ARM
June 2021
Recommendations to help prevent swimmers from suffering shallow water blackout in your pool

Could the following situation occur at K-12 school, college, or university?

A strong swimmer at your school or campus pool swims laps underwater to increase his lung capacity. Lifeguards pay little attention to him and focus on weaker swimmers. Another lap swimmer notices the underwater swimmer lying motionless at the bottom of the pool. By the time lifeguards pull him from the pool, the swimmer has drowned in water only a few feet deep.

Sadly, this scenario has occurred at several institutions. The cause is shallow water blackout (SWB), which occurs when swimmers hold their breath underwater for prolonged periods.

Ten people in the U.S. drown every day, according to the Centers for Disease Control and Prevention. And most lifeguards and pool administrators know drowning is a common hazard. But many don’t realize that drowning kills not only weak swimmers but also good swimmers in pools staffed by lifeguards.

What Causes Shallow Water Blackouts?

Breathing lets the body inhale oxygen and exhale carbon dioxide. As the body’s level of carbon dioxide increases, it triggers a natural impulse to breathe.

Many swimmers who hold their breath underwater learn they can stay under for longer if they breathe rapidly or take deep breaths before descending. The swimmers mistakenly believe rapid or deep breaths increase the amount of oxygen in their lungs.

This activity doesn’t actually add much oxygen to the lungs; it significantly decreases the body’s carbon dioxide, which suppresses the body’s impulse to breathe. While holding breath underwater, these swimmers misinterpret the lack of impulse to breathe as a signal that their oxygen level is sufficient. Instead of surfacing to breathe when oxygen levels drop, they black out. If they’re not discovered quickly, they typically inhale water into the lungs, convulse, and die of cardiac arrest.

Training Aquatics Staff

Aquatics staff, including lifeguards, pool managers, and coaches, must understand SWB and how it results from underwater breath-holding exercises and games. the American Red Cross and the Y include information on the dangers of prolonged breath-holding in their lifeguard manuals, but the message doesn’t always get through.

Monitoring for SWB is challenging. Lifeguard training programs generally focus on surveillance and rescue techniques for weak and struggling swimmers. Because those who fall prey to SWB are typically strong, experienced swimmers trying to improve or demonstrate their underwater swimming prowess, lifeguards who don’t understand SWB may not appreciate the dangers.

Another practical challenge for lifeguards is detecting a swimmer experiencing SWB. While movies may portray drowning victims as flailing around, screaming for help, and struggling to stay afloat, the reality is usually different. Typically, SWB occurs underwater, where a struggling swimmer can’t be easily seen. Many training programs miss the mark, teaching scanning patterns and other drowning concepts that emphasize the pool’s surface rather than its bottom. Even in crystal clear water, a swimmer at the bottom of a pool can go unseen due to reflections, glare, and refractions at the water’s surface.

Most SWB victims are found motionless underwater and, in some cases, victims’ arms and legs may move involuntarily in a swimming-like motion as they lose consciousness. Often a swimmer wearing goggles, not the lifeguard, is first to notice an SWB victim’s body underwater.

To help lifeguards, many public pools have installed Poseidon, a computer-aided drowning detection system. The system uses computer vision technology and a network of cameras mounted above and below the pool’s surface to analyze underwater activity and alert the lifeguard in seconds of a swimmer in trouble.

Even if they trained on SWB, lifeguards shouldn’t agree to supervise anyone who wants to engage in prolonged underwater swimming. Submersion for even a half minute can lead to drowning. Guards owe attention to all swimmers, so keeping special watch over a single swimmer engaged in endurance breath-holding isn’t appropriate. Because many water safety training programs don’t address SWB directly, consider providing supplemental training on the subject or retain an independent expert to do so.

Managing Your Aquatic Facility

Many SWB incidents occur in a swimming pool rather than at a beach, lake, or other natural setting. Because pools provide a predetermined path and distance, they’re particularly attractive to swimmers setting goals for underwater swimming or challenging others to do so.

Protect swimmers from the dangers of SWB by improving your pool facility and managing the activities of those who use it. Review the rules and regulations governing pool use, examine your facility’s layout and equipment, and consider taking these steps:

  • Prohibit prolonged underwater breath-holding. If a swimmer is underwater for more than a few seconds, lifeguards should jump in and force the swimmer to the surface.
  • Use clear, prominent signs to indicate underwater breath-holding is prohibited. The most effective signs display the universal symbol for breath-holding.
  • Don’t let lifeguards keep a special watch over any swimmer. Lifeguards should refuse to do so if asked and be prepared to explain why your pool prohibits underwater breath-holding.
  • Immediately recover any swimmer sitting or lying on the bottom of the pool. Do this even in shallow water. It only takes seconds for a swimmer’s underwater activity to lead to serious injury or death.
  • Ensure lifeguards maintain a clear view of the total facility. They should use a guard stand or rove the facility as needed.
  • Install a computer-based drowning detection system. These systems are designed to act as the lifeguard’s “third eye,” detecting and notifying the lifeguard of a body coming to rest on the pool’s bottom within 10 seconds.


More From UE

Checklist: Swimming Pool Safety

Additional Resources

Resources on Shallow Water Blackout

Shallow Water Blackout Prevention

Aquatics International: Playing It Safe

Clarion Water Safety Signage

Sample Institutional Pool Regulations

Massachusetts Institute of Technology

Scripps College

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