Can you elaborate? As others are saying this can be extremely dangerous. Normally I wouldn't just reiterate other comments but if it might save a life can't hurt to be sure.
That is still hyperventilating in a technical sense, as is the breathing you're doing for a minute beforehand; both will result in lowering your CO2. If you're actually holding your breath and going under water, please take an intro freediving class. So many people die every year just because they don't have the basic safety training necessary to turn this activity from extraordinarily dangerous to quite safe.
