Using SCUBA is the key point.
If you breathe in a full breath of air at c. 10 m depth, which is at c. 2 atm, hold it, then rise to the surface suddenly, this will want to double in volume and will cause severe lung damage. This is why divers always keep breathing, never hold your breath.
OTOH, if you fill up at the surface, then dive to 10 m, the air compresses by x2, then if you surface quick, it is back to 1x volume, and everything is ok. There is no concern when not breathing pressurized air.