@Wilso,
I've never dived myself but have known one serious diver. He was doing major deep sea diving in the thirties, apparently invented some equipment, and, friend of my dad's, they were both army air force colonels, would come to our house for dinner sometimes. So I sort of grew up on his stories. (John Craig, wrote Danger is My Business at some point later; that book, I think I remember, about many divers).