Shallow Water Blackout: The Silent Killer Of Swimmers

Jun 21, 2014; Santa Clara, CA, USA; Start of heat two of the Women's 50M Freestyle during the preliminary heats at George F. Haines International Aquatic Center. Mandatory Credit: Bob Stanton-USA TODAY Sports
Photo Courtesy: Bob Stanton-USA TODAY Sports

Commentary by Jeff Commings

Most competitive swimmers believe they are invincible. If they can survive a 10,000-meter workout during the holiday break or do a 2,000-meter butterfly set and ask for more, then nothing can stop them.

Unfortunately, that is not true.

With the research indicating that underwater dolphin kicking is faster than swimming on top of the water, athletes feel the need to add more underwater kicking to their daily workouts. When University of Texas men’s swimming head coach Eddie Reese said he started every workout this past college season with some underwater dolphin kicking, I’m sure every coach said “We’re going to do that, too!” Sometimes, the goal is to reach the 15-meter mark. Other times, athletes will push past it and challenge their teammates to see who can kick the furthest underwater.

In many cases, a swimmer will stay after practice to do some extra credit work on underwater dolphin kicking. That’s what happened to Louis Lowenthal in 2012 when he stayed after practice with the North Baltimore Aquatic Club to improve his kicking work. Though lifeguards were on the deck, it’s understandable to think that they didn’t need to watch him closely, as he was a very accomplished swimmer.

A few minutes later, a lap swimmer noticed Lowenthal motionless at the bottom of the pool. He was pronounced dead later that day, the victim of shallow water blackout. It’s caused when oxygen levels in the brain get drastically low, and carbon dioxide in the body is even lower, often due to hyperventilation before submerging. The low level of carbon dioxide is the catalyst for shallow water blackout, as it’s often too low to signal the brain to tell the body to surface. Once oxygen is depleted, the swimmer faints underwater and drowns.

Lowenthal’s death was a catalyst for Bob Bowman to use his stature in the swimming community to educate his fellow coaches about shallow water blackout. While he spoke with his peers at the 2014 American Swimming Coaches Association’s world clinic about the silent killer, Dr. Rhonda Milner was walking the halls with an equally important goal.

She wanted people to know about, which was created to educate people on the dangers of hypoxic training. I spoke with Milner at the clinic about her son’s death in 2011 due to shallow water blackout, and her tips on recognizing when someone is in danger of passing out underwater.

Rhonda Milner’s SwimmingWorld.TV interview, September 2014

In the eight months since we posted that interview, action has been taken around the world. USA Swimming, British Swimming and Swimming Australia were a few national federations to issue statements warning coaches and swimmers about overdoing it on underwater kick training. Swim teams have responded with social media messages and letters to families about safely training to be great underwater kickers. With the cooperation of USA Swimming and the Michael Phelps Foundation, Milner created a public service announcement last winter to help kickstart the education process.

USA Swimming public service announcement featuring Bob Bowman and Michael Phelps

“Unfortunately it’s taken more deaths to get more recognition, because these were deaths that were totally preventable,” Milner said.

Sunday is the first National Shallow Water Blackout Prevention Day, which is part of National Water Safety Month. It’s perfect timing, with public pools opening across the country for the summer season.

“We wanted to bring some more attention to shallow water blackout and try to raise awareness and educate,” said Milner, who created the national day through her Shallow Water Blackout Prevention organization. “We thought it would be a good way to close out the National Water Safety Month. We are hopeful that this will … lead to a lot of more people realizing that prolonged breath holding should be banned in public pools.”

An article by the Reuters news agency reports that New York City and Santa Barbara, Calif., have taken steps to ban breath holding in their public pools. Signs admonishing the act have been posted, and lifeguards have been trained to know what to do when they spot breath holding at their pool. Statewide bans are also being considered, Milner said, thanks to a report by the Centers For Disease Control and Prevention that highlighted the risks of prolonged breath holding.

Though the above PSA says competitive swimmers are most at risk for shallow water blackout, recreational swimmers can also die from it. Though many of the causes of drowning are simply due to someone not knowing how to swim, some are caused by kids who dare their friends to a breath-holding contest. Not wanting to lose, one of them will push their bodies past the limit, when their brain shuts down before it tells the body to go to the surface. The scary thing is that shallow water blackout can happen in as little as three feet of water, and happen so quickly that even the most experienced lifeguard might miss it.

I agree with the critics in the Reuters article that say lifeguards can’t spot every swimmer holding their breath underwater at a busy rec pool on a summer day. But knowing the signs helps their chances of recognizing it. The lifeguards at a pool that I use regularly walk around the edge of the pool about every10 minutes, looking down into the water. For a long time, I never knew what they were doing. To relieve my curiosity, I asked a lifeguard about it.

She said a recent audit by the city parks and recreation department showed them that the lifeguards have a limited field of vision at their posts, and that some swimmers are not easily visible to them, even if they are sitting as high as 10 feet above the pool.

A new policy was created to have a lifeguard check along the edge of the pool regularly, especially in the wake of an incident in which a man nearly drowned. Though it was partly due to his weak heart condition, he had also been doing limited-breathing swims. The lifeguard on duty didn’t notice it immediately, but another lifeguard was walking by the man’s lane at that moment and noticed his swim gear on the deck, though no one appeared to be in the lane. That lifeguard peeked underwater and saw the swimmer motionless on the bottom. Luckily, the staff was able to revive him after a few minutes, but he had suffered minor brain damage after being underwater for about 20 seconds.

“If the other lifeguard hadn’t been walking by, the man would have died,” the lifeguard said.

There’s more work to be done to educate the public about the dangers of shallow water blackout, but the attention is spreading quickly. We at Swimming World have written numerous articles on shallow water blackout prevention, and it’s a topic that we will always support if it means saving more lives in the pool.


  1. Conner Andrews

    im sorry, but as a competitive swimmer that has to unfortunately do a large portion of my training on my own during “open swim”, we don’t need to blow this up. after i was done swimming for the badgers, they stopped allowing underwater training at the university open swim and even had a sign for it that also included no hypoxic training. people like me don’t need more training obstacles. it takes an idiot to not know when it is time to come up for air. i understand the dangers for others, but all i see is prevention of this kind of training which is necessary.

    • Cuyler Gabriel

      It doesn’t take an “idiot” not to know when it is time to come up for air!

      If you hyperventilate your body will be telling you, you don’t need air when you actually only have seconds left.

      That is why it is such a danger because it can take anybody at any moment because Co2 levels will fake you body out.

    • Cuyler Gabriel

      Dont think you want to call victims of shallow water black-out idiots

      Some have been revived quickly enough and I think the only knowledge they were lacking at the time was that of SWB and clearly you are too.

      Help save more!!! Dont just think the stupid ones will die! Goodness

      Its happened to some of the most technically advanced, mentally tough and highly trained athletes like yourself and they are no loner with us.

    • avatar

      Dear Mr Andrews,

      First, I am literally incensed that you are even inadvertently inferring that my son WAS an idiot. He drowned on August 1, 2014 in the Bahamas as a result of hypoxic training after spear fishing all day. He was 27 years young, a Master SCUBA Instructor and Rescue Diver with over 1,500 logged dives. He was never taught about the dangers of prolonged breath holding or he would not have been doing what he was doing that killed him. He was doing this after having sailed his 30 foot sailboat from northern Vermont to the Eleuthera Islands. No idiot can do that Mr Andrews!

      We are all trying to save lives and for you to use the term “idiot” in your rebuff to our message is an insult of the highest order. If you want to educate yourself and not just throw painful insults go to Perhaps you will gain some respect for causes of Shallow Water Blackout and what it can strip from your arms in a heartbeat!

      Dean E. Haller
      Live Like Benjo Foundation

    • avatar

      I’ve never met a stupid Navy SEAL. Not one. Yet several of them have died from shallow water blackout.

  2. Brooks Richardson

    In my humble opinion~~this has been an athletes red line training issue for ever. Case in point, some athletes push themselves to the point of collapse. Ever see at the finish line an athlete lose bowel controle, or pass-out, crawl a few yards to get across that line? In Swimming the athlete is making that same mental effort, pushing the envolope with a deminished ability to get rid of bad air to replace good air. (hyperventlation) causing fainting. That is more apperant in swimming than other sports.~~~been their done that when in High School swim practice repeat 50 freestyle sprints on short rest I passed out and needed to be rescued by my team mates and coach. At 16 years old I was dead for awhile I’m told. ( i have no memory of the incident other than passing out.)

  3. avatar

    I disagree. Swimmers that do their research and learn what the hell they are about to do, know the signs. And if you are smarter, you bring a buddy that watches you underwater with a snorkel. Just another obstacle for me with the pools in my area as I try and train for the military. Thanks.

    • avatar

      A young man I coached was training for seal school and blacked out. Lifeguards saved him and after weeks in the hospital he is currently serving. this young man is smart and was in excellent condition. No one is immune or invincible.

  4. Katie Faggiano

    Rob Faggiano beating the issues to death

  5. Laura Ensley

    Swimmers and coaches alike take heed. These deaths are preventable.

  6. Bethan Aldridge

    lung busters? Sarah Clarke Edward Jackson Mason Jones Emily Milsom??

  7. Kathy Holthe

    Great article. Brings back scary memories!!

  8. Maria Dudley

    Nan! Our panic with underwater kick no breathers was totally justified. Thank god nothing happened to us or the other girls.

  9. Kristen Sokol

    Renee McGregor, the danger is real hahaha

  10. Peter Scott

    In performing underwater training in elite athletes they should be paired up. One observing one performing. No underwater training should be performed without one on one supervision to avoid SWB. Stay safe.

  11. Ahmed Ali

    One valuable life 🙁

  12. avatar

    Water is very important for swimmers!

  13. Eva O

    Rebecca Keating god this is scary

  14. Merk Fam, Jennifer Regh Brunetti, Melissa King Dorencz, Melissa Michelic Martin, Greg Pryor

  15. Jessica Lynn

    I have swam for 25 yrs. this was my favorite thing to do, under water sets!

  16. Daniel Pires

    Andrew TavcarScott McGintyPat Orkins see this is why you guys shouldn’t do under waters

  17. avatar

    R.I.P. Louis Lownethal.
    God bless his sister Lillian and the rest of his family.

    Live Life Like Louis!

  18. Carla Hanson

    I am former swimmer now freediver. Freedivers train breath hold and always with a buddy. This prevents any accidents from happening. It is not about not training in apnea; it is about not ever training apnea alone !

  19. avatar

    I betting lots of swimmers have been killed in traffic accidents driving to workout or meets, we need to ban driving to save our swimmers

  20. Sarah Roberts

    Mandy McCollough Johnson Kenslei Senn

  21. Ronald Hehn

    And you think you know the biochemical reason for this phenomenon haha! Not a laughing matter …

  22. Kevin Rieffel

    Safety during hypoxic exercise is very serious. I was disappointed to see it boiled down to a clickbait headline for a sponsored Facebook ad. Et tu, SW?

  23. Ryan Mason

    Austin Heaton, read up on this before life guarding this summer

  24. Phil Fons

    Tyler LeRoy please don’t kill yourself

    • Tyler LeRoy

      Yeah I saw something on this the other day. That’s why you don’t do that kind of training by yourself. It’s definitely freaky how easy it can happen though.

    • Phil Fons

      Ya, I never really thought about it before reading the article, I know you guys get the proper safety training beforehand but I can imagine a lot of club/highschool/college swimmers do not

  25. This is no joke. Very serious. Synchronized Swimmers are at risk for this, too. My daughter’s unconscious body was pulled out of the pool after a prolonged breathold at the end of a long synchro practice. The coaches were watching closely and got her out in seconds. She regained consciousness and did not inhale any water. I still cry when I think about it.

  26. Morgan McCafferty

    Abby Wilson don’t die like this while we are in college lol