I've felt some narcosis at depths as shallow as 130 feet, but it is unusual that I feel anything until 160 feet. However, one particular dive, I came upon my buddy (we have a very loose buddy team when spearfsihing) and he had shot his spear into a rock. The 5-ft long shaft was some how horribly lodged into the limestone rock, with the flooper tip deployed (open up) after some penetration of the rock.
As I approached I could seem him working feverishly trying to slam the shaft back and forth as violantly as possible. Both he and I knew he would destroy the speartip, but the shaft might be salvagable. I decided to watch for a few moments, since watching people destroy gear and try to remedy mistakes they have made is kinda funny (both above and below the water).
This is extremely strenuous work and he was busting ass and swearing.
After a little while, he gave up on the in/out slamming motion and now tried to rotate the shaft , he quickly bent the crap out of the shaft which instantly made the whole effort futile (snce he must have already destroyed the tip and a bent shaft is worth zero).
Instead of abandonment, he continued to furiously slam the shaft back and forth, twist it, bend it. Whatever...I totally lost it, this was perhaps the funniest thing I had ever seen in my life!
I somehow inhaled some water and started a violent and uninterupted coughing attack. Still, I just watched and continued to laugh my ass off with my mask half filled with water. After about a minute, I began to realize that I really was not breathing enough, I was just choking and laughing at his predicament. I had absolutely no concern for my safety at 130 feet; I have done similar dives hundreds of times, so I was not stressed at all at this depth.
Finally, I realized that I was begining to drown, that this was NOT humorous and I had better stop laughing and start to really concentrate on clearing my airway. It was not until that moment that it popped into my head that I must be narced (stoned) and THAT is why this scene was so funny. The idea had never even closed my mind before that narcosis was afecting me.
I concentrated on coughing and breathing and stopped laughing and was fine within 30seconds. Narcosis is like that for experienced divers, if everything is going fine, you may not notice anything.
50 meters is way too deep for an inexpereinced diver and 60 meters is enough to really ring your bell. Some people would become incapacitated at that depth.