[irowe]

Having also found the hyperventilating approach effective, I just want to note for other readers that hyperventilating before breath-holding is extremely dangerous when swimming or diving. This is heavily emphasized in safety trainings for swim coaches. It greatly increases your chances of hypoxic blackout: https://www.socom.mil/POTFF/Pages/Hypoxic%20blackout.aspx

[klyrs]

Oh wow, that's fascinating. Good thing I've never been interested in diving, especially free-diving!