so Rick....why were you asking the question in the first place? out of general interest or you are planning of diving AIR below 30m?
General interest in where peoples limits are. Personally I don't like narcosis at all and try not to dive below 30m unless on trimix. Note I said try, sometimes logistics dictate otherwise . There have also been plenty of references to the difference between say 30m, 1m viz, 10c water and 60m, 40m viz,28c water. I have dived the Coolidge to 60m on air and even with the good conditions was not comfortable past 45. Also noticed a considerable deterioration in the functional ability of other divers. Who dives AIR?