Hyperventilation (and freediving danger)

Hyperventilation is breathing too fast before you go underwater. It tricks your brain. This happens when you take many rapid breaths to blow off carbon dioxide. While people think this helps them stay down longer, it actually removes the primary signal that tells your body to breathe.

This process is dangerous for freedivers because it can lead to a shallow water blackout. In 2021, I saw a student nearly pass out after rapid breathing at a pool in Koh Tao. Their CO2 levels were too low to trigger a gasping reflex before they lost consciousness.

Never use rapid breathing to prepare for a dive. Just take slow, natural breaths until you feel calm. If you feel dizzy, stop immediately. Most blackouts happen because the diver ignored their body’s natural signals.