Rapture of the Deep

In preparation for my trip to the Caribbean next semester, I spent this weekend taking a class to learn how to SCUBA dive. My class and I learned all about the necessary equipment, what to do in emergency situations, and how to stay safe while SCUBA diving. We also learned about the physics of pressure, volume and density, so that we could better understand what happens when you descend into the deep. This inevitably led to a conversation about Nitrogen narcosis.

Nitrogen narcosis, or “rapture of the deep”, is a condition in which the symptoms resemble those due to intoxication by alcohol. Divers experiencing nitrogen narcosis lose their decision making abilities, their focus, and their judgment, coordination and multitasking skills become impaired. What could this potentially mean for the diver? They could ignore safe diving practices because they feel invulnerable to the dangers of their surrounding environment (sounds a bit like the actions of those individuals who are intoxicated by alcohol).

While the mechanisms of narcosis are not fully understood, it is believed that the change in pressure due to depth has an impact on it (most cases are not reported until descent around 100 feet, and immediate relief from symptoms can be acquired simply by ascending a few feet). Nitrogen dissolves more slowly in the blood than other gases, which is thought to affect the permeability of the lipid bilayers of neural cells. The Meyer-Overton hypothesis states that narcosis is due to Nitrogen gas penetrating the lipids of the neural cells, which is thought to interfere with the transmission of neural cell signals. Further research has indicated that the gas induces an increase in volume of the bilayer, which disrupts the membrane environment and modifies cell responsiveness.

Luckily for me, I am only certified to dive to 60 feet, so I shouldn’t experience any complications due to Nitrogen narcosis. I’ll just play it safe and get drunk off alcohol instead.

Lavoute, C., Weiss, M., Rostain, J-C. 2005. Effects of repeated hyperbaric nitrogen-oxygen exposures on the striatal dopamine release and on motor disturbances in rats Brain research 1056(1):36-42.

Schwerzmann, M., Seiler, C. 2001. Recreational scuba diving, patent foramen
ovale and their associated risks Swiss Medical Weekly 131:365-374.


  1. ctenotrish, FCD says

    Just so long as you don’t drink and dive . . . .

    And I must say, based on experience, that diving when dehydrated and hung-over is just a way to ruin an otherwise excellent way to spend a day.

  2. savagemickey says

    I lost a good friend to nitrogen narcosis. She was a new diver and was with a group that went to the Caribbean on their first diving trip. Their experienced local dive leader got nitrogen narcosis and swam down to his death and my friend and another woman followed him and perished as well. They never found their bodies. Happened back in ’88 or ’89. It got quite a bit of press around the Twin Cities.

  3. Todd says

    Nitrogen narcosis is also jokingly called “Martini’s Law” which roughly states that for every 1 atmosphere absolute (1 ATA, 33 FSW) past 60 feet it’s equivalent to having one martini.

    I don’t think ascending just a few feet will completely relieve the effects of nitrogen narcosis – like all narcotics it’s a dose-response function so while ascent might make you feel better your performance is still impaired. I used to work in hyperbaric medicine and would often get the opportunity to (safely) go to 165 feet in a chamber and experience narcosis. I just got a little light headed and somewhat goofy but I knew one girl who’d laugh uncontrollably.

    Interestingly, narcosis is sometimes put to good use as a means to help control high pressure nervous syndrome which is encountered at very high pressures and is believed to be caused by compression of the cell membrane which interferes with nerve function. Since narcosis can counter this effect it lends support to the hypothesis that nitrogen increases the lipid bilayer volume (i.e., counters the compression).

  4. Josh says

    My whole family dives. My brother experienced nitrogen narcosis once. He was oddly lucid during the experience. He related that he kept seeing gnomes on the bottom of the quarry we were in, but he knew he was experiencing nitrogen narcosis, knew it wasn’t real.

  5. Pablo says

    For some reason, I am reminded of the old Mad Magazine treatment of Scubadiving…

    “I have ‘Rapture of the Deep'”

    to be compared with

    “I have ‘Rupture of the Groin'”

  6. says

    It can take significant time for the extra nitrogen that dissolves in extravascular fluid to escape once you surface. There is an increased chance of decompression sickness (nucleation of bubbles in bodily fluids) on experiencing the low pressure of air travel immediately after diving at depth.


  7. says

    PZ – welcome to the world of diving! Just a note on pronunciation; in hounour of Cousteau it should be pronounced “ze Rapture of ze deep”.

    More seriously I agree with ctenotrish about dehydration. With narcosis I find that when I start to get narked it makes me worry a lot more than usual so I compulsively check my gauges every minute or two and generally become a lot more aware of potential issues (and focus on them). I read somewhere this is a fairly common manifestation of narcosis (and I guess probably the best of the forms to get).

    Have fun divin’ – whereabouts down here in the caribbean are y’all headed.

  8. Jim Baerg says

    I’ve heard that this occurs with any inert gas, & the greater the molecular weight the lower the pressure needed to cause narcosis. So helium is used for deep diving & it’s possible to use Xenon as an anesthetic at 1 atm.

    I’d be interested in more detail on this if anyone knows more.

  9. Grewgills says

    From my experience (somewhere north of 1000 dives) there seems to be considerable differences in susceptibility between individuals. My buddies and I frequently did reverse profile dives of 150′ or more and noticed no intoxication as long as we remained calm and did not exert ourselves much at depth. I know others that regularly felt mild narcosis when diving below 100-115′.

    I was mildly narced once doing vigorous activity at about 110′. I felt a mild euphoria, some butterflies in my chest and realized what was going on. I stopped and relaxed for a few minutes and it passed. The only other time I was narced was at about 175′. In this case we had planned to do a reverse profile dive and swam out to where we could barely see bottom and incorrectly assumed that we were in about 100′ of water and dropped without checking our gauges until we hit bottom. When we hit bottom and looked at our gauges we immediately began our ascent along the reef slope and the intoxication passed after I ascended 5′ or so.

  10. says

    Welcome to the club! Diving is a great experience, as long as you’re careful. As noted earlier in the comments, drinking and diving is not recommended. Drinking in moderation /after/ you dive is probably OK, but consumption of alcohol prior to diving is believed to be a contributing factor to DCS.

    Best general source of medical information on diving is the Divers Alert Network (http://www.diversalertnetwork.org/). DAN is a terrific resource, and one every diver should know about (or belong to).

    But most important, as a diver, you can now pay visits to your cephalopod friends! Some of my best dives ever have involved just floating and watching cuttlefish. Can’t recall whether they live in the Caribbean, but you should certainly find reef squids and possibly octopi.

    Have fun!!!

  11. Ken Shabby says

    SCUBA? It’s been around long enough that it’s now a common noun, like radar, sonar, laser, and lidar.

  12. TomDunlap says

    It’s going to take time for it to sink in that PZ’s not the only one blogging here now. Anyway, welcome to SCUBA, Lua Yar.

  13. John Farrell says

    Years ago I tried a beginner’s class in Mexico, and had a sudden resurgence of childhood claustrophobia just putting the equipment on, so my hats off to anyone who’s mastered the art.

    (it was the part where they make you take your mask off underwater, put it back on and then blow the water out with your nostrils)

  14. Eisnel says

    My one experience with nitrogen narcosis was pretty fun. It was a deep dive for my advanced certification, so the whole point was to go down and experience nitrogen narcosis (I was maybe 15 at the time, so I had never been drunk). A commenter pointed out that experienced divers claim to develop an immunity to it, which I imagine is similar to how experienced drinkers (drunks) require more alcohol to get intoxicated. Our dive master told us to stay right behind him. That was a good thing, because I couldn’t really concentrate on my surroundings at 120′. I remember thinking that I was just a tiny point of existence trapped within my mask, which made me a bit claustrophobic (so I’ll agree with the poster who suggested that it can cause you to get a bit paranoid). The effect might be more like being high than being drunk. But I didn’t do anything crazy, like try to tear my mask off. It’s just a good thing I didn’t have to make any decisions; following my dive master was about all I could do. Once we started to ascend, the effect went away pretty quickly and I was able to think rationally again, and pay attention to my surroundings.

  15. says

    Have fun diving, Lua Yar. It’s a fun sport. But, keep in mind that there are other, even more dangerous, things to be wary of—like not holding your breath, especially while surfacing. (My own dive instructors recommended always breathing: either very slowly inward, or very slowly outward. You’re supposed to breathe slowly anyway, so that works out just fine.)

    I’m sure (or at least I hope) they talked about this topic. Humans aren’t evolved to properly sense extra pressure in the lungs since it doesn’t happen under any natural circumstances. If you hold your breath while surfacing, you can easily give yourself an embolism without ever even feeling any danger. And, you die right there on the spot. Dive partners can do nothing about it, unlike they could potentially do if they noticed you were narc’d. (This can easily happen within the first 60 feet of depth, too.) This also applies to rescuing others who may have passed-out at depth: while swimming them up to the surface, it’s important to keep them vertical and their head tipped back so that air can readily escape. Otherwise, you can achieve exactly the opposite of your goal by virtually guaranteeing their death on the swim up.

    Presumably, they also taught you about hyperventilation and the fact that you can pass-out without ever even sensing that you’re short on oxygen, too, right? (The urge to breathe is triggered by an excess of carbon dioxide in the blood, not by a deficiency of oxygen. Under normal circumstances, these are largely equivalent—but not under all conditions, such as hyperventilation.)

    Anyway, these things aren’t things to freak-out about, but they are still vitally important to keep in mind. (You know, like not driving with your eyes shut. :p) Humans aren’t built for underwater habitation, so there are some additional precautions for which we must consciously account, since our bodies don’t automatically do them for us.

    But, all that being said… have fun! It’s a beautiful world down there! :)

  16. Niobe says

    You might want to look into Nitrox.

    However, I never got the need to dive below 30 meters, after that it’s more of a penis length contest, kind of like coming up with a 3 digit bar readout. “Sure I feel like throwing up and my head is splitting but I’ve got 110 bars left. You got 70? Ya pussy”.

    I just got back from my 6th Bali dive vacation. Manta rays, sea snakes and the elusive Mola Mola, and blasting off some Japanese divers from the corals with my under water air horn. Fantastic all around.

  17. says

    I suppose I should mention that one of my dive instructors told us about a time she got narc’d and was holding out her regulator to the surrounding fish, offering them a breath. lol

  18. woozy says

    I was going to comment that nitrogen narcosis seems safer than alchohol in that it it goes away instantly as you go higher to lower pressures… and my scuba instructor said he kind of liked it. Then I read the horror stories of post #2 et al.

    I don’t know. I’ve never been deeper than 80 ft.

    I suppose I should mention that one of my dive instructors told us about a time she got narc’d and was holding out her regulator to the surrounding fish, offering them a breath. lol

    LOL indeed! That’s the funniest thing I’ve read in a long time!

  19. David Schoonmaker says

    Re: Grewgills post (#9), my experience as well. Further, different people seem to respond in different ways. I’ve been narced on perhaps 15 occasions, and it just makes me nervous as hell. On one dive with my dad over the wall at Andros in the early ’60s, he got disoriented and headed down instead of up. (This seems a common reaction.) I grabbed his fin and got him going the right direction. As you can imagine, that only increased my anxiety diving deep with him.

    As someone else noted, there’s really little recreational reason to go deep enough to risk nitrogen narcosis, and I haven’t been deeper than 30 meters since the ’60s (grew up and got some sense). Most of what’s interesting to see is in the first 10 meters. In fact, I generally prefer free diving.

  20. Fernando Magyar says


    “Presumably, they also taught you about hyperventilation and the fact that you can pass-out without ever even sensing that you’re short on oxygen, too, right?”

    Also known as Shallow Water Blackout. This would be more likely to be a danger if you are doing breath hold diving and not SCUBA diving.

    Welcome to the wonderful world of diving Lua Yar! As someone who has been doing this since 1975 I’m an ex CMAS instructor and was certified 500ft Sub Sea Oil HeliOx and currently I ScubaKayak with a club off of Fort Lauderdale Florida I have one word of advice to you, do not let any of the previous comments scare you off. If done correctly SCUBA is extremely safe. Just know your limits and never exceed them. Be safe and enjoy the underwater world.

  21. Bride of Shrek says

    After diving for years I got narked once at only 18 metres and it was completely unpredictable and without warning. I remember it being the most pleasant experience very much like being drunk. I clearly remember wanting to go deeper and sucked a fair bit of my tank by singing “Final Countdown” really loudly to a moray eel. Basically acting so moronic that my dive buddy was more than aware what was happening and got me out of there. I have no doubt if my buddy hadn’t been experienced or if I’d been diving alone (never, never) I would have died because I truly thought I could breath under water at that point.

  22. autumn says

    Slightly off topic, I have experienced a shallow water blackout while simply swimming a few inches below the surface. If you actually know that the panic state of needing a breath is just a kind of suggestion, you can go far enough to put yorself into real trouble.

    “A little knowledge is a dangerous thing/drink deep or know not the whatever whatever”

  23. Fernando Magyar says

    Re: #25,
    While it is certainly possible to experience (SWB) in a swimming pool, the term “Shallow Water Blackout” refers to a very specific cascade of physiological events.”Shallow water blackout (SWB) is the sudden loss of consciousness caused by oxygen starvation following a breath holding dive.”


  24. Pablo says

    .”Shallow water blackout (SWB) is the sudden loss of consciousness caused by oxygen starvation following a breath holding dive.”

    So blacking out from panic in the shallow end of the baby pool is not SWB? OK, then I can safely say that I have not suffered from SWB.

  25. bernarda says

    As a long-time diver myself, I advise going beyond just the beginning course and take an advanced if at all possible. You will find it is worth it.

    However, most of the interesting stuff is in the first sixty feet so if you stick to that you will have a good time.

    If you go to tropical areas, one good rule of thumb is “don’t touch anything”, especially off Australia. There are some dangerous and almost invisible creatures down there.

  26. ajay says

    However, most of the interesting stuff is in the first sixty feet so if you stick to that you will have a good time.

    Don’t believe their lies… wrecks can be found at any depth, and the deeper ones are often in better condition (no battering from surface swell). Shallow wrecks are the best for marine life, though; instant reef.
    And don’t stick your head into a crack in the rock to get a closer look at the moray eel that lives there. (Seen it done.)

  27. JW Tan says

    Don’t poke jellyfish either. Don’t try to swim through wrecks if you don’t know them well. Don’t carry free rope or line underwater. Don’t hold your breath (unless you’re really deep and narked).

    So many rules… but ultimately worth it.

  28. Bride of Shrek says

    But do feel free to piss in your wetsuit. Nothing better on a cold water dive than a little “self-warmth” to keep you going.

  29. Lurchgs says


    Um.. you are making an assumption here – that wrecks are the only things worth looking at.

    I started diving in.. um.. well.. a while back. At virtually any realistically depth in the ocean there’s something to see (assuming you are on bottom – free swimming stuff tends to go away as you go down)

    So far, I’ve never narked… and it can be really tempting at the bottom of some rivers and quarries.


    Lua Yar – aside from the most obvious advice (be very careful), I fully agree with the commenter who suggested you get at least advanced. With the advances in technology and the like, requirements for various levels of diving proficiency have relaxed since I learned, and – no matter the technology – I think over all it’s a bad thing.

    Water is pretty and friendly in the shower, but any depth sufficient to cover your nose makes it a hostile environment. It is far better to be overly cautious. Get as much training as you can, then dive at a lesser skill level

    If you are on any medications – OTC or prescribed, have your doctor check to see if they have altered effects at pressure. It’s *probably* not needed.. but you never know. (once, one of my dive team started a new med, without checking, and he ended up hospitalized – at 40 feet)

    Further, I completely disagree with the commenter who suggested that alcohol after a dive is ok. While it depends on depth and time on bottom, etc, I would wait 3 or 4 hours at a minimum before I imbibed.

    Final caution, take nobody’s word about your equipment. Not even His Imperial Squidness, PZ, or an instructor. (but, your instructor probably told you this one)

    SCUBA is hellish fun, and insanely addictive. I hope your trip and dives are as fun as my early dives were.

    Last, but not least .. this got me some very strange looks way back in 19^&$%^& After my first open water dive, the instructor asked for feedback on the experience. The Ex Navy UD (Underwater Demolitions) expert nearly lost his eyebrows in his hairline when I equated the experience to sky diving. I ran into him a couple years later, and he let me know that in a class a few months after mine, an Army Ranger had made the same comment. Apparently, not many people do both (though I’ve stopped jumping – SCUBA is easier on these old bones) -but those that do seem to solidly equate the two experiences. When you get back, you should give it a try (not that there are any Danio Rerio at 10,000 feet)