The Martini Effect in Scuba Diving

Nitrogen narcosis is often compared to being drunk

Scuba diver playing with a glass bottle underwater.
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The Martini Effect is a slang term used in scuba diving to refer to nitrogen narcosis, the physical and mental impairment experienced by scuba divers on deeper dives.

The high partial pressures of nitrogen experienced by divers on deeper dives has an anesthetic effect on the brain, it can cause a sense of euphoria, impair motor abilities and coordination, lead to poor judgment and reasoning, and in extreme cases, prevent the diver from remembering much of the dive.

Why the Funny Name?

Nitrogen narcosis has been compared to being drunk, and with good reason!  Many of the effects are the same. Clearly, nitrogen narcosis can be dangerous to divers and has been implicated in many incidents and accidents. You wouldn't drink and drive, and you shouldn't get narced and dive either.

The name is cute, and the experience of being "narced" on a dive may even be pleasant, but make no mistake. Nitrogen narcosis is seriously dangerous. 

At What Depth Will I Experience the Martini Effect?

The deeper a diver descends, the stronger his narcosis will be. This is how the term The Martini Rule originated. Divers have said that every 30 feet/10 meters of depth will have have the effect on a diver of drinking one martini.

Most divers won't feel the effects of narcosis at 30, or even at 60 feet. However, the analogy holds true. Some divers feel nitrogen narcosis at shallower depths than others, much as some people get drunk more easily than others.

Research has shown that all divers are at least partially impaired at 100 feet/33 meters and below. Even if a diver doesn't notice the effects of narcosis, they will experience impairment of judgment and reasoning in novel situations.

Avoiding Narcosis

The simplest way to avoid narcosis is to limit your depth. A diver who descends no deeper than 60 feet (the recommended depth limit for open water certified divers) is extremely unlikely to ever feel the effects of narcosis.

During the Advanced Open Water Course, divers experience their first deep dive under the supervision on an instructor, and this is an excellent way to test your self and your susceptibility to narcosis in a safe and controlled manner. Keep in mind that many additional risks are associated with deep diving, and recreational divers who plan to dive deeper than 100 feet/30 meters would do well to take a Deep Diving Specialty Course.

Technical divers, however, regularly descend well below 100 feet. They do so safely by reducing the percentage of nitrogen in their breathing gas mixture by substituting a less narcotic gas, helium, for some of the nitrogen. This type of gas mixture is known as trimix and requires technical diving gear and training to use safely. 

The Take-Home Message About the Martini Effect in Scuba Diving

The term Martini Effect makes narcosis sound fun, and sometimes it is. However, just like being drunk, nitrogen narcosis impairs a diver's ability to think clearly and act in a coordinated manner.

Thankfully, divers can avoid nitrogen narcosis by avoiding deep dives, or can reduce the risks of narcosis with training and practice under the watchful eye of a professional scuba instructor.

Divers who want to go beyond the recreation depth limits of 130 feet/40 meters can do so safely by enrolling in a technical diving course.