Is it true that hyperventilating bad for you?

I will deal w only: One type of hyperventilation. Hyperventilation prior to breath hold dives or swims. A diver blows off co2 by hyperventilating to over-ride the mechanism in the body that stimulates breathing when the co2 level rises. It is done to ^ time underwater. Breath hold capacity has bragging rights in the diving community. Here's the problem - you can black out & lose consciousness or even die.