I have heard about the rule of thirds for free-diving http://freediveuk.com/the-freediving-breath-hold-rule-of-thirds/. Assuming that I don't hyperventilate before breath hold underwater swimming and I start getting a tiny burning urge to breathe on my chest at 1 minute, would I black out after 3 minutes of being underwater? If I could get through stages one and two in the rule of thirds, would I get to the third stage when I hit 2 minutes? Assuming I resist the urge to breathe on my chest with all my might and keep on holding my breath underwater, would I have little oxygen in my whoe body, in the blood, lungs, and spleen at minute 3, since little oxygen to the brain can cause unconsciousness?