All I am saying is what they were teaching 40 odd years ago when I got my ticket. What we were taught then was based on the US navy dive tables. If only fools dived to 200' with air, so be it. We obviously were all fools and we (all my friends and associates) all survived the experience. Just because dive recommendations have changed over the past 40 years doesn't change history and the way diving was taught. And, for what it's worth in the early days we didn't have BCDs. CheersOxygen is toxic at much less than 300 feet. And frankly, you won't find anybody but a few fools still doing deep dives on air anyway. Trimix is the way to go, and hypoxic trimix is THE thing for deep diving, if you're not rich enough to dive heliox.
Bounce dives are also pretty foolish, which is one reason why the recreational limit is 130 feet. That depth gives a short but reasonable bottom time while staying within the no stop requirement of rec diving. It's also a function of the near-universal adoption of the AL80 (an aluminum cylinder carrying 80 CF of air) as the default tank. Even 130 feet on a single AL80 with an average SAC (Surface Air Consumption) rate is pushing it, since you probably will NOT have enough air in your tank at the end of your bottom time to bring you AND your buddy to the surface without bending (or breaking) the ascent rates.
Nitrogen narcosis is a misnomer. Pretty much all gases cause narcosis to greater or lesser degrees when under pressure, so it's called gas narcosis now. While narcosis CAN be an issue on shallow dives, it's most commonly encountered below 100feet. And there are plenty of people who don't experience it until even deeper. We routinely do mental testing with puzzles (math problems on a slate, opening a combination lock, that sort of thing). I've gone to 155 feet on air (in a no current freshwater cave in Mexico) without being measurably affected. I wouldn't have done THAT dive on air, had it been in cold water or a current. And I'm not one of those fools who is going to do deep diving on air anyway. With the right gas mix, narcosis can be virtually eliminated on much deeper dives, and decompression obligations drastically reduced.
But this is pretty much off topic. The point is that it is not at all difficult to document a claimed 2000 year old find in 200 feet of water. Since it's not documented, I think it's safe to say it doesn't exist.