The air we breathe is 21% oxygen 78% nitrogen and 1% other stuff. For scuba diving increased pressure at depth on boards more nitrogen in your body than normal so when you surface that extra nitrogen can form bubbles in places which shouldn’t have bubbles and that can lead to injury/ death.

Scuba diving is a lot of fun. I encourage a9nyone vaguely interested to ho to their local scuba shop and do a demo dive.