Learning to breathe is the most important part of free-diving practice. The way of staying in the water longer is to practice breathing slow and deep. Divers breathe in for 5 seconds and breathe out for 10-15 seconds. To avoid over-breathing, they breathe out for a long time more than breathing in. Free-divers practice how to breath in the water, and they can start free-diving when they have a pulse under 80/bpm.