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THESE ARE JUST TWO OF THE CLAIMS made last year by the Diving Diseases Research Centre (DDRC), following research to determine if divers can tell when their performance is being affected by nitrogen narcosis.
As this research was carried out in the controlled environment of the DDRC chamber, we decided to carry out our own research, based on your thoughts and feelings on the subject.
We posed the question: "Narcosis, fact or myth?" on the DIVERNET website. The replies we received were startling and supported the researchers' claim that "narcosis is not simply an objective measurable phenomenon - it also has a subjective facet".
Our intentionally broad question elicited a wide range of replies which, not surprisingly, had a common theme surrounding the effects of narcosis at a variety of depths and conditions.
There were also those of you who simply didn't believe that you suffered narcosis, even at depths of 70m on air. In addition, a large number of your replies described in vivid detail the types of narcosis you had experienced.
One of the more disquieting replies came from Mark Chase, who described a dive at the Azure Window in Gozo.
His buddy had been ill in the morning and, despite his being sick a few times, the pair decided to dive with a planned depth limit of 40m.
For some unknown reason, Mark's buddy changed his mind during the dive and went beyond the 40m limit. Mark followed, but at 61m decided to stop as, "if he wanted to kill himself, he wasn't going to take me with him."
Mark watched his buddy descend to 66.5m before he turned back. He described the time before this change in direction as "agonising", but this wasn't the worst part of the dive.
Mark explained how his heartbeat sounded like a bass drum and how he was "convinced I wasn't going to make it out". Luckily, both divers made it safely to the surface, but Mark never understood what had happened down there.
Following an unnerving experience in a "large quarry in North Wales," Ian Horridge described narcosis as "very real and very dangerous". He said he tried the "narcosis puzzle at 50m". While trying to solve that puzzle (to spot the differences between two divers and two mermaids), Ian outlined how he felt fine one minute and then had a "complete blackout".
He described the moment when he came round: "I was spinning around and completely unaware of what was around me, and I couldn't locate my buddy." Fortunately for Ian, he recovered as fast as he had blacked out and, on rising to 35m, managed to "sort things out and calm down."
Blacking out could be a far more common experience than you might have thought. Mike Ormrod had "a moment of terror" at the Thomas Canyon in Sharm el Sheikh. It all started at 56m, where "I thought I had blacked out". This was followed by a sudden feeling of loneliness, leading to being "petrified that I might lapse into unconsciousness and sink into the abyss". Mike managed to control his feelings and, on ascending to 50m, regained control of his dive.
These incidents describe the more sinister side of narcosis, perhaps the precursor to the fatalities suffered by all too many divers. As Sam Harding from DDRC commented: "Narcosis is without doubt a factor in many diving incidents, where they often develop into something more serious."
The deeper your narcosis, the more unusual it tended to be. At 50m, Glynn said he had an out-of-body experience, while Stephanie Reigiss claimed that on a dive to 48m she was followed by two men who were trying to kidnap her.
It was only later that she realised that they were her buddies, and when they eventually managed to catch up with the fleeing Stephanie, they had to take hold of her and forcibly cause her to ascend. At 40m, her sense returned.
These examples of blackouts and altered states of consciousness are a clear indicator that narcosis is a real phenomenon. However, we did receive several replies from divers who simply were not convinced.
For some, narcosis is still a myth. Or are they just the lucky ones who have suffered narcosis but, on ascending, have lost all recollection of their symptoms?
Mark M is a part-time divemaster who believes that "as with many divers, I can say that I have not felt the effects of narcosis". Paul H, another diving instructor, also considered himself immune from any such condition. "My deepest air dive was to 66m, to a site where there is a cathedral-shaped arch. I remember sitting on the sand watching the light through the gaps while humming a Tom Petty song, thinking: ÔNarcosis? What's all thefuss about?'"
When I pointed out that this sounded like a hallucinogenic trip, he replied: "That's how I am at any depth. There definitely wasn't any narcosis."
Pierre Farrugia from Malta is a deep-air diver who does recognise the existence of narcosis but doesn't believe that it really affects him.
"Normally I dive on air for 25 minutes, with little effect from narcosis. Once I even dived to 70m on air, and although I could feel that I got slower, I could do my dive and easy tasks."
I found these responses chilling - these are experienced divers who should recognise the effects. The cause of this lack of belief may be what the DDRC calls "confusion about when the effects of narcosis are to be expected..." as "an accurate depth of onset has never been satisfactorily proven".
The replies also indicated that the effects of narcosis could occur at any depth. Paul Watson "refused to swim up the slope" after doing a dive to the 30m-deep hydrobox at Stoney Cove. Geoff described an incident in which he had to assist his wife at 24m with a buoyancy problem: "I looked down at the weightbelt and the buckle was not there... after my wife explained the situation on the boat, the weightbelt was picked up and the 'missing buckle' was pointed out to me."
Will Swift had a problem at only 20m with a delayed SMB. The task he had to perform involved creating a loop and then clipping the reel to a handle.
He couldn't perform this simple task, despite knowing what he had to do and trying it 10 times. Eventually, his buddy had to come to the rescue.
Operating a delayed SMB also caused Digs and her buddy some concern, as they spent 15 minutes trying to tie a knot that had come undone.
Once they both reached the surface, they couldn't work out why they had spent so much time incurring a huge deco penalty when they had three back-up SMBs.
Colin Bridges had what could have potentially been a disastrous narcosis hit during a wreck dive to 36m, after a long descent due to painful ear clearing. As he passed 30m, "it felt like a number of vodka and cokes had kicked in - I was spaced out".
His buddy had asked him to shine his torch in a hole. He did so, but was completely unconcerned about why he was doing it and what there was to see. His narcosis even reached the point where he stayed on the seabed while his buddy went to the deck at 30m. He clearly remembers thinking: "If my kit fails, I'm not worried." Once his buddy came to collect him and took him to 30m "the fog cleared and I thought, what the heck just happened?".
At just 20m in Stoney Cove, Martin Wilkinson found his "head spinning... I was afraid of the water above me". Once he had recognised this feeling as narcosis, he managed to calm himself down.
For some of you, narcosis has been a very weird experience indeed.
Roy Francis described how on a night dive to 20m he heard an old-style telephone ringing for about a minute, while Simon P was so convinced that he didn't have a buddy at just 25m that when he reached the surface on his own, he still couldn't remember having one until the buddy started shouting over to him.
If some of these experiences sound bizarre, it's because they are.
Although the medical world accepts that narcosis exists, the reason why the absorption of nitrogen at pressure causes these symptoms remains a mystery.
Sam Harding told me how nitrogen binds to lipids in the bloodstream and, "as two-thirds of the blood that comes from your heart goes to your brain, depending on the neural pathways and blood-flow structure what gets hit first depends on the individual - it could be your sense of vision or touch.
"Medical science still doesn't know why narcosis happens, it just knows that it does."
After discussing this area further with Sam, it became apparent that the type of narcosis you may suffer depends on the individual. The analogy would be: different dreams - different narcosis.
What we didn't expect from our survey was the way many of you classified your narcosis.
Despite your numerous individual descriptions, we've attempted to group and label the types of narcosis you have experienced.
While the Black Out category has already been dramatically portrayed by divers above, Andrea Casey illustrated what we have called the Dream category of narcosis.
During a dive through a tunnel that started in 36m and finished in 45m, Andrea experienced the sensation of falling before reaching the entrance - once she had secured herself by focusing on a fixed point, she entered the crack in the rock, where "the walls began to throb red and I felt quite spaced out, as if almost in a dream".
Her guide recognised her "dopey grin" and took her up a few metres, where the dream ended.
Another category of narcosis in your replies was of Visual Changes. Simon Powell explained how his narcosis was usually preceded by "a perceived visual narrowing - peripheral vision becomes less obvious and my focused field of view gets smaller and smaller".
Helen said she sometimes suffered a "don't give a monkeys" form of narcosis, an example being when she let her gear drag along the seabed at 50m.
Others talked of similar experiences; in several of these instances you just aren't bothered about your kit and how you care for it. We've decided to call this the No Worries form of narcosis.
Helen also described a "nagging mum" category, where she started "telling my buddies to hurry up". This form was quite common in your replies and can be best categorised as Anxious narcosis. While the urban myth of narcosis has led us to believe that sufferers may do silly things such as "saying hello to the fish", the reality of Anxious narcosis is far more sinister.
Nigel H's breathing rate always increases, followed by feelings of claustrophobia and panic. His buddy recognises the physical symptoms and helps him ascend. However, on some occasions Nigel has had to abort the dive, as his breathing rate has climbed and wouldn't go back down.
Gary Cornell's form of Anxious leads to him feeling, "disorientated, panicky and paranoid", resulting in incidents such as a 35m dive on which he bumped into a ridge and thought it was "another diver messing with me".
Anthony Servedio from Washington State dives regularly in the dark waters of Puget Sound, where he often gets the "ping of a weird anxious situation", although on warmwater dives to the same depth he feels nothing.
While the Anxious form of narcosis provided some quite terrifying symptoms, the one form you mentioned but didn't seem too worried about was Memory Loss narcosis. Nigel H explained in graphic detail how his Anxious narcosis affected him, but he ended by saying "there are many dives where I was probably narked, but I just don't remember them".
Although Mark M was convinced that he had never suffered from narcosis, he did go on to mention: "I know there is a saying that if you say you haven't, you have." Will Swift, who earlier described his narcosis at 20m with a delayed SMB, then went on to say that he had "been to 70m on air without problems".
An argument for those divers who claim that they don't suffer from narcosis at these depths is that they did, and they're lucky to be in a position to tell the story. Have they simply suffered from Memory Loss narcosis to such an extent that they can't remember any part of the dive on which they were affected?
The Memory Loss form of narcosis isn't just about forgetting what happened, however. Lisa found that on a dive to 40m in a dark and rough sea, she "could not remember how to swim and had to keep hold of the shot".
Lisa also described how narcosis causes her to feel "fuzzy-headed - I have to concentrate a lot harder to do the dive." This seemed a very apt descriptor for another category, that of, what else but Fuzzy Head?
On a 70m air dive at Reqqa Point in Gozo, Mark Chase experienced this "nice fuzzy narcosis", with symptoms such as hearing his own heartbeat and a "whaaaaa noise in my ears". At a more sedate 25m, Nicky Langley from Qatar feels narcosis starting to affect her when "my head gets cloudy... my whole body buzzes... it is like a warm fuzzy glow on the surface of my skin."
Another peculiar form of narcosis is the Seeing Things/Not Seeing Things category. Belinda from Bermuda was so convinced that the fish at 45m were doing somersaults that she raved about this newly found phenomenon at the surface. Martin Wilkinson saw a turtle at 35m at Skomer Island in Wales, then seemed to come to his senses and see it as a shark. Only when he had a seal pulling at his fin did he realise what he had really seen.
Martin also described how, on a dive to 35m on UB74, his buddy pointed to a hole: "I saw a prawn, not very interesting... she called me back and I saw several prawns, fascinating, the third time she called me back, I saw the enormous conger that nearly filled the hole!"
One of the most frustrating forms of narcosis you reported was the Fixation, and in most cases it involved computers. Gordon Baron became totally confused about how deep he was on a 38m dive, and then went on to become completely disorientated when he mixed up the dive time and no-deco time.
Gordon pointed out that he didn't feel any of the effects of narcosis until he started checking his computer. Will Swift made a similar miscalculation, when he mistook deco time for the no-stop time left, despite the numbers increasing.
Ken McQuilton was quite bewildered when he couldn't make sense of the depth, time and deco figures at just 30m. On all these occasions, the diver's reports indicated that they had become obsessed with the computer's readings.
We had no shortage of replies making the comparison between narcosis and the category of being Drunk, with some of you taking this one step further with our final category of Mischievous. Some examples came from Simon Powell, who thinks to himself: "I shouldn't be here, tee hee", and Ian W, who at 35m forgets the consequences of "playing hide and seek behind rocks, as well as looking for things to move"!
While the variety of categories of narcosis surprised us, we weren't ready for the claims raised that went on to stump the scientists. Tom suggested a link between dyslexia and narcosis; James Garland believed that narcosis may also be influenced by CO2 levels; and Anne, a diving instructor of more than several years, quoted three cases of women who had suffered more with narcosis during their periods, even at the shallow depth of 15m.
I asked Sam Harding about these phenomena. "People with dyslexia may find it more difficult to change their coping strategies, so suffer more," she said. "As for CO2 retention, while it is the nitrogen that causes narcosis, the levels of CO2 in the blood may play a part in how and when narcosis hits you."
James had already espoused the theory, based on his own research, that any kind of physical pressure leading to changes in CO2 levels could account for the unpredictable nature of narcosis.
This theory was supported by Brian Edge, who suffered from a frightening form of narcosis on a 42m wreck dive he had done several times before.
On each occasion he had not suffered from narcosis until he tried to move the shot-weight. "My head became light and dizzy... my vision was getting distorted and, on ascending, my vision became like a dark green screen in front of me. As soon as I hit the top of the wreck - clear vision."
Sam said she had also heard various anecdotes from women who reported the onset of narcosis when they were having a period and said that this would be "a very interesting study to do".
She suggested a number of other interesting areas for narcosis research in the future, everything from adaptability and diving-up (progressively working up to a deep dive over several dives) to the effects of rapid compression.
The only thing certainty about nitrogen narcosis is that it is real, even if no one really knows why it happens.
As Sam stated towards the end of our conversation: "We still have a lot to do if we want to fully understand what factors contribute to nitrogen narcosis."
What is certain is that a small group of divers would be well-advised no longer to view narcosis as a myth, or something that happens only to other people. For the majority, healthy respect for its effects might just cut diving incidents.
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Mark Chase watched his buddy descend unexpectedly to 66m
Martin Wilkinson saw turtles and sharks, not seals
Gary Cornell had a fight with an underwater ridge
Andrea Casey found tunnel walls throbbing red
James Garland reckons CO2 levels influence narcosis
Lisa, founder of the Fuzzy Head school of narcosis
Simon Powell thinks to himself: "I shouldn't be here, tee hee"
Ken McQuilton couldn't make sense of his computer
expert Sam Harding says that narcosis is a factor in many diving incidents
Nicky Langley experiences "a warm, fuzzy glow"
- Don't be pressured into doing any deep dive where you are likely to become overly anxious (how many divers go out of their depth on liveaboards "because I've paid for all the dives and I'm going to do them")?
- "Dive up" to any deep dives, ie, do each one progressively deeper. This technique is used by the Navy, though there are no guidelines for the time period over which this should take place.
- Use only equipment with which you are familiar on any deep dive - a 40m dive is not the place to try out new kit.
- Consider a slower descent rate - there is some indication that a fast rate can bring on sudden narcosis.
- Attain a level of confidence in any new environment before going deep - a 40m dive in the Red Sea may be less narcosis-inducing than a 40m dive off the coast of Scotland.
- Practise your drills so that they are second nature. One of the biggest narcosis-inducers is task-switching and coping with the unfamiliar.
- Don't dive deep on air! The BSAC limit for air diving is 50m and for good reason. So why are so many of you diving on air between 50 and 70m?
- Plan the dive and dive the plan. How many dives have you planned to go no deeper than 35m but ended up at 40m-plus?
- On any deep dive, have a plan for the onset of narcosis. As soon as you feel its onset, start to ascend. Don't wait for it to develop into Anxious or Blackout narcosis. If you're suffering some form of narcosis, it is highly likely that your buddy is too.
- Talk to regular buddies about their experiences so that you can watch out for symptoms in them and they can do the same for you. Discuss contingency plans in advance.
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Black Out, Dream, Fuzzy Head, Seeing Things, Mischievous - your answers to our questions about nitrogen narcosis have helped Brendan O'Brien to identify at least 11 distinct forms of this little-understood diving condition. 
