"always dive with a buddy" Actually that was a hot subject for debate even 25 years ago, because divers tend to DIE in pairs as the result of buddy diving. USCG, DAN, all found that time and again, one diver gets in trouble, the buddy either tries to help or gets involved, and both die. Of course there are no stats on 'saves' so there is only debate, but I think even PADI (the 'certificate of the day' folks) offer a "solo diving" certificate now.
Diving has radically changed. Back then, most divers used the WW2 USN tables--and ignored the fact that those tables were "warm water, no wetsuit needed, prime healthy male" tables. At a seminar given by a USN diving medical officer, I asked "And since we all need wetsuits here, aren't we supposed to move up one interval in these tables?" and I think the room was shocked when he said "Yes, or use the cold water tables."
Now everyone is hooked on computers (which may be more accurate but probably eliminate some safety margin inherent in the conservative tables) and "Nitrox" which probably is a good thing--but nowhere near the big deal the marketers would make of it. (Hey, it's still "air" and if you use the appropriate table, what's the big deal?)
My instructor was indeed a veteran ww2 "frogman" who told us that simply inhaling, holding a deep breath, and shifting from a horizontal position to a vertical one (in the water) could cause enough of a pressure change to blow out some lungs. Not typical--but possible. Someone with no training at all, could still get into trouble with a "mild" compressor in a situation like that.
So..."just" using a compressor at ten feet, shouldn't be a problem, but still could be a danger for some folks.