A rebreather dive begins before you enter the water. You strap on the machine, put on your mask, or pinch your nose, and “pre-breathe” the unit for five minutes while monitoring the sensors and heads-up display (HUD) for any signs of trouble. It’s usually one of the last checklist items to complete before commencing the dive depending on the rebreather.
It’s the silence that first catches the attention, as you descend in the water column. There are no noisy bubbles. You can hear the soft whisper and rhythm of your own breathing and almost detect the beat of your heart. You relax and slow down.