This was first described by Jaques Cousteau as the “raptures of the deep” and later termed nitrogen narcosis. Narcosis when diving is the change in thinking and awareness, sensory and motor function and behaviour that occurs at depth. Breathing gas at depth leads to narcosis, often noticed around 30m it can be an issue from around 20m and below.
Narcosis is not well understood
Divers get narcked due to breathing gases, such as nitrogen, at depth. The deeper we dive, the more nitrogen (and other gas) is taken into the body. There are a few different theories about why this changes our mental and physical abilities, but no one really knows. What is agreed is that the gases affect the nervous system including the brain. They seem to affect the nerve cells in a way that interferes with how messages are sent around in the brain and to other parts of the nervous system.
Being narcked can be hilarious…
Divers sometimes behave really strangely when under the influence. They think strange thoughts and do bizarre things. Stories include: trying to give a fish a regulator so they could breathe, fleeing from buddies believing them to be kidnappers or removing all of their equipment and attempting to send it to the surface. It changes how you perceive things and can make fish and crabs seem really funny.
… but dangerous
Our thinking ability, awareness and judgment are all affected by narcosis. Working out problems can take longer and we are more likely to make mistakes. Add to that the odd behaviours and unconsciousness, narcosis poses a real risk to our safety.
Narcosis is unavoidable at depth
We are all experiencing gas narcosis when we dive. In the same way you can’t drink a pint of beer and not be under the influence of alcohol, you can’t dive deep and not be narked. Gas narcosis can only be avoided by diving shallower.
We are not always aware of narcosis when diving
It is not predictable
Depth is the main factor, but it is not the only one. Environmental conditions such as visibility, water movement and temperature can make a difference because of the stress they place on the diver. The nature of the dive and the tasks to be completed may have an effect. It would also be interesting to look at psychological and social variables.
Gas narcosis affects different divers in different ways. Any diver may be more or less affected at the same depth on different dives.
We can adapt to narcosis when diving
It is generally thought that we do not become physically more tolerant of narcosis, just that we adapt our behaviour. The most straightforward way to avoid narcosis is to dive shallower, and set a personal depth limit. But frequently you find that divers exposed to narcosis find ways to deal with it. That does not mean not being narcked. Divers can apply useful strategies, but they are still under the influence.