system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: how can free divers hold their breath for so long without causing brain damage?

If it only takes 4 minutes without oxygen to cause brain damage, how can they stay underwater for 4+ minuets and not hurt themselves.
gpt
The brain isn't without oxygen when they dive, they are relying on residual oxygen in their lungs, blood, and tissues.

Consciousness is very expensive and generally a lack of oxygen will put them to sleep well before permanent brain damage occurs.