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- Depth makes me anxious and I do not recognise narcosis
What is happening
In deeper water, anxiety can show up as a wish to stop the descent, narrowed attention or an urge to ascend. Narcosis can resemble intoxication, with impaired judgement, poor concentration, drowsiness, euphoria or fear, and the diver may not recognise it.
Why it happens
Ordered from the most common cause down. Open one to see the mechanism behind it.
As depth increases, so does the narcotic effect of the gas. Individual susceptibility is unpredictable and can vary between dives.
- greater depth
- individual susceptibility
- repeated descents
Carbon dioxide has its own effect on the central nervous system and can intensify narcosis. At depth, higher gas density increases the work of breathing.
- overexertion
- insufficient exhalation
- increased gas density
Fatigue, cold and anxiety can make thinking and fine motor control less reliable. These factors add to the risk of narcosis rather than being offset by experience.
- lack of sleep
- physical exertion
- inadequate thermal protection
Some medications and substances can potentiate narcosis. This is not for self-assessment before a dive; it requires medical advice.
- benzodiazepines
- antihistamines
- opioids or cannabis products
What to try on your next dive
One thing, not ten. Give it a full dive before you judge it.
Depth plan with your buddy
- Before entry, agree with your buddy on a conservative limit based on certification, conditions and your personal state.
- Name in advance the signs you will treat as possible anxiety or narcosis, and agree the abort signal.
- During the dive, make brief mutual checks of orientation, normal behaviour and readiness to return.
- If there is a symptom or concern, use the 3 Cs: concede, communicate and follow the pre-agreed plan by ascending slowly to shallower water and not descending again.
- Make your first returns to deeper water gradually, in easy conditions and without task loading.
- If you need to practise impairment at depth, do so only as part of a course with an instructor.
How you will know it is working
| Published reference | Value | Source |
|---|---|---|
| Conservative narcosis threshold | 30 m or shallower when tired or anxious | PADI — Nitrogen Narcosis: What Divers Need to Know |
| Recreational limit on air | 40 m | PADI — Nitrogen Narcosis: What Divers Need to Know |
| Buddy observation | especially important below 21 m | DAN 2004 DCI Report |
Record planned and actual maximum depth from your computer, as well as whether the conditions and how you felt stayed within the pre-agreed limits.
- Do not descend deeper if you suspect narcosis; ascend slowly to shallower water until you recover, and do not descend again.
- Do not dive deeper than your certification, plan and conditions permit. The recreational limit on air is 40 m, and 30 m is the more conservative threshold when tired or anxious.
- If symptoms do not resolve after ascent or worsen, end the dive and seek medical assessment for DCS or AGE.
- Do not assume you will reliably recognise narcosis yourself; your buddy may see the change before you do.
- Do not confuse narcosis with DCS; they are different conditions.