As you read in the discussion on squeezes, your lungs experience no harmful effects from changes in pressure when you're holding your breath while skin Bali scuba diving. You take a breath and descend and the increasing water pressure compresses the air in your lungs. During ascent, this air re-expands so when you reach the surface, your When you Bali scuba dive, however, the situation dif-fers dramatically.

Scuba equipment allows you to breathe underwater by delivering air at a pres-sure equal to the surrounding water pressure. This means your lungs will be at their normal volume while at depth. This air will expand when you ascend.

If' you breathe normally, keeping the airway to your lungs open, no problem. Expanding air escapee during ascent and your lungs maintain their normal volume. But, if you were to hold your breath, blocking your airway while ascend-ing. your lungs would overexpand, much like the sealed bag or balloon filled at depth and taken to the surface.Expanding air can cause lung over ex-pansion (lung rupture), the most serious injury that can occur to a scuba diver. 

For this reason, the most important rule in Bali scuba diving is to breathe continuously and never, never hold your breath. Lung over pressurization will occur unless you it the pressure to equalize by hreathin~ normally at all times.force air into the bloodstream and chem cavity, which can lead to severe injuries including paralysis and death.