Even the best swimmers are not drown-proof, and Shallow Water Blackout can be the cause.  I’ve had some inquiries about Shallow Water Blackout recently which led me to develop a list of resources.  I thought I’d share them here, starting with a description of the issue from 

http://shallowwaterblackoutprevention.org and http://shallowwaterblackout.org.uk then a list of the other top resources.  Please let me know if you have more resources to add to the list - the more information the better!

A Shallow Water Blackout is brought on when:

the body has been working extremely hard - exercising lowers the oxygen level in the body;

by taking deep breaths in preparation to swim under water, the body expels carbon dioxide from the lungs;

the body’s desire to breathe is brought on by a build up of carbon dioxide in the lungs - we breathe carbon dioxide out to breathe oxygen in;

the lungs have reduced levels of carbon dioxide, and this fools the brain into thinking that there is not yet the need to breathe;

the brain is low on oxygen from the initial hard exercise and this brings on a faint.

On land, this faint would send oxygen racing to the brain and ‘bring round’ the patient.  However, in a swimming pool the swimmer inhales water, and without immediate aid will subsequently drown.

Who can be affected: It can affect anyone that is breath-holding, even the physically fit swimmer. It is especially seen in competitive swimmers, Navy SEALs, snorkelers, spear fishermen or anyone who free-dives. SWB cuts across the spectrum of freediver training affecting all levels.  No one is protected from succumbing to SWB.

When it can happen: Frequently, Shallow Water Blackout occurs without any warning of its onset. In fact, because of the hypoxia and detached mental state one can feel euphoric and empowered to continue breath-holding. Unlike regular drowning where there can be 6-8 minutes before brain damage and death, there is only about 2 ½ minutes before brain damage and death occur because the brain has already been oxygen deprived coupled with warm water as in swimming pools, hastening brain death.

Where it can happen: Shallow Water Blackout can occur in any pool, lake, ocean or body of water when breath-holding, regardless of water depth. Even if lifeguards are on duty there is still a great risk because it is hard to detect from above the water.

Knowledge is power - help spread this knowledge please.

Resources:

National Swimming Pool Foundation.

The ILSF policy statement.

Signage from Clarion Safety.

Aquatic Safety Research Group videos.

Dr. Sanjay Gupta on CNN.