Hyperventilation works because the urge to breathe comes from rising carbon dioxide in your body, not from low oxygen. The three on four breaths drop your body carbon dioxide levels below normal, so when you hold your breath it takes longer for the levels to rise high enough m trigger breathing.

If you've never tried it, you may be amazed how Well hyperventilation works - but it's important that you limit it to only three or four breaths. Excessive hyperventilation – more than three or four breaths - can be dangerous because you can lower your carbon dioxide levels so far that your body runs out of oxygen before you get the urge to breathe. This would lead to sudden unconsciousness - with –out warning - and drowning. Don't hyperventilate excessively.

Besides limiting hyperventilation to three or four deep, rapid breaths, rest a minute or so between breath-hold dives so your body can restore its normal oxygen level. If you feel fatigued, dizzy or light-headed, stop diving down. Float, relax and rest.

You may be familiar with unintentional hyperventilation, which results from anxiety or -tress, and causes someone to breathe rapidly Old shallowly. This leads to respiratory difficulty, and contributes to the overexertion and air starvation problems you learned about earlier. By using proper diving techniques, you'll normally avoid this, but if you find yourself reacting to stress and anxiety with rapid, shallow breathing, force yourself to stop, breathe slowly and relax.