Breathing nitrogen under pressure has an anaesthetic, alcohol-like effect that grows with depth. It's commonly noticeable from around 30 m and increases the deeper you go.
Narcosis impairs judgement, coordination and reaction time. It's reversible — ascend a few metres and it eases quickly.
Managing it
- Plan conservative depths and ascend if you feel impaired
- Dive well-rested; cold and CO₂ build-up make it worse
- For deeper diving, train in the appropriate techniques and gases