Just be careful when using hyperventilation for diving. You can drown. Might pass out before you feel the urge to breathe. https://en.m.wikipedia.org/wiki/Free

Just be careful when using hyperventilation for diving. You can drown. Might pass out before you feel the urge to breathe. https://en.m.wikipedia.org/wiki/Freediving_blackout https://en.m.wikipedia.org/wiki/Freediving_blackout That said, it's hella effective. Used it a lot as a kid snorkeling in the Mediterranean. Only swallowed water a few times.