This is the crux of what i find wrong with your methods. The more narced you get the harder it is to know how impaired you really are. By the time you realize that you are beyond your limits it's usually to late to preemptively thumb the dive and you are already starting down into the incident pit.
Please keep your divers safe and be honest with them. I'm out.
Is this something that you have experienced or are you parroting someone else? I've done hundreds of air dives below 175 ft and many more in the 110 to 130 range.
I think the point is that everyone needs to find where "their limit" is, so YOU DON"T EXCEED IT. I have no problem with some people setting their limit at 100 feet (even though it would be ridiculous for me).
Personally, I generally feel no effects down to around 130, at 160-170 I often will feel it, but other times I will sense no impairment at 170 ft (even though I have to constantly remind myself that the inability to sense the narcosis, is probably a symptom of it).
As the the depth exceeds 190, the narcosis is evident and I need to double check my decisions, move slow, avoid exertion if possible and remind myself that I am stupid and I should probably not try anything I haven't done hundreds of times before.
I generally don't like to exceed 200, but I've functioned quite well down to around 225 ft. Deepest air dive, was about 289 and I was very wasted ( a one-time stupid stunt). I've also, totally exerted myself and got pretty wasted at 190 feet (numb lips and tongue, perceptual narrowing, sound of breathing and bubbles screaming in your head, etc.)
Personally, with deeper air dives, I think the diver needs to learn to manage their respiration, work load and carbon dioxide levels more than worrying about being 10-15 feet deeper than normal, or if they are feeling buzzed or not. Getting totally out of breath at 190, can really get your head spinning and I find it tough to catch my breath at that depth. If I get exerted, it is pretty much time to bail. Divers need to learn that they have much less physical strength reserves to deal with problems as they get deep on air. These are the important lessons, rather than harboring an excessive fear of narcosis itself.
I remember I did a very relaxed, solo, drift dive to around 200-210 a few years ago and was not trying to kill fish. Warm water, 125 ft visibility, just an observation dive, no speargun, very unusual for me. It was just so simple and easy without trying to do any work or having the mental stress of worrying about sharks. I sensed minimal narcosis and I can remember everything about the dive (as best I can remember
)
I've had no training in technical or deep air diving, so these are just my personal observations.
