Shallow Water Blackout

Shallow Water Blackout is brought about by reduced levels of carbon dioxide in the lungs, fooling the brain into thinking there is not yet a need to breathe. Swimmers/freedivers/snorkellers can suffer SWBO when entering the water after heavy exertion prior to swimming or hyperventilating (expelling carbon dioxide from the lungs) prior to swimming underwater. The Shallow Water Blackout Factsheet (at right) has been produced by www.shallowwaterblackout.org.uk in order to raise awareness of this silent killer.