 Narcosis is potentially one of the most dangerous conditions to affect the scuba diver below about 30 m ( 100 ft ) . Except for occasional amnesia of events at depth , the effects of narcosis are entirely removed on ascent and therefore pose no problem in themselves , even for repeated , chronic or acute exposure . Nevertheless , the severity of narcosis is unpredictable and it can be fatal while diving , as the result of illogical behavior in a dangerous environment . 
