SWB
Shallow Water Blackout
By Michelle Brislen
What is SWB?
 Loss of Consciousness while in water
 Usually caused by hyperventilation while
freediving or breath-holding
 Often happens to freedivers, athletes,
and good swimmers.
 Can happen in the ocean, pools, lakes,
rivers, etc.
“Hero Worship”
Image from NY Times
Energy Processes
QuickTime™ and a
decompressor
are needed to see this picture.
Cellular
Respiration
C6H12O6 + 6O2
Sugar

Oxygen
6CO2 + 6H2O + Energy
Carbon
Dioxide
Water
How does it happen?
 Release of CO2 (Carbon Dioxide) through
hyperventilation or deep exhales
 When under water O2 (Oxygen) is used up
and turned in to CO2
 CO2 is lower than normal because of
hyperventilation thus decrease urge to
breathe
 Stay down/under water longer and O2
continues to be used and deprives brain
 Blackout occurs
Normal
Dive
SWB
Dive
Problem

Diagrams from Wikipedia
Shallow Water Blackout
Diagram from Aquatics International
How to Prevent SWB
 Do not hyperventilate
 Do not have breath-hold competitions under
water
 Do not perform underwater laps
 When you feel the urge to breathe, begin your
ascent “Leave something in the tank!”
 Dive with a Buddy!!!! Maintain watch for 30
seconds after surfacing
 Be weighted correctly and willing to release
your belt if you’ve pushed it too far.
 Tell your friends! Adults too!
References
 shallowwaterblackoutprevention.org
 “Confessions of a Freediving Spearo” by Sheri
Daye; Hawaii Skin Diver Magazine 2010
 www.aquaticsafetygroup.com/PDF/DyingforAi
rAquaticsInternationalFebruary2005.PDF
 www.aquaticsafetygroup.com/PDF/ShallowW
aterDeathTheCombatEdge2003.pdf
 www.wikipedia.com