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Comment by pinkmuffinere | Hacker News Reader

I know very little about either of these worlds -- can you explain why that is such a dangerous thing to do? Is it just that you might run out when you don't expect to?

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Lung over expansion injury if he holds his breath on ascent like many free divers naturally do. He was taking compressed air breaths at depth and then ascending. If you fill your lungs at 33ft and ascend, the gas will double in volume at the surface, causing tons of damage and bleeding.

Breathing pressurized air from a tank while you're under pressure in the water can dissolve extra nitrogen into your system, as you ascend the nitrogen can bubble out in your blood stream causing nitrogen narcosis aka the bends https://wikipedia.org/wiki/Decompression_sickness

Nitrogen narcosis is a different thing than the bends.

That's not the problem with this. When you inhale from a scuba regulator, you're breathing in air at ambient pressure, which means an extra one atmosphere of pressure at 30 feet depth. As surrounding pressure drops, that air will expand proportionally. If you take a deep breath and then ascend, the air can overinflate your lungs and cause serious damage. SCUBA divers are trained to exhale while ascending to avoid this, but freedivers tend to hold their breath.

I don't know how you could hold your breath with double the volume in lungs. That at only one atmosphere.

Not to mention your ears. Part of releasing air as you ascend is to help your ears adjust. Its only natural. Same with descending.

I have seen alot of minor injury as a summer dive boat mate. Mostly blood vessels burst in the eyes from people holding their breath ascending..

I saw a guy pop out of the water like a cork because the ran out of air. Of course he said he was Navy UDT. Didn't need a buddy. Steel doubles and a speargun. Thankfully nobody got hurt.

NAUI Diver with over 45 dives in Hatteras.

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