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'Exhale-and-Sink' Diving in PNG

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sebastien murat

Well-Known Member
May 18, 2004
Recently returned from Papua with mixed results:

Initially hoped to continue phase II of breath-hold diving experiments looking at gas-exchange (testing narcotic potential with depth) and breath-hold diving beyond residual volume. This was to be done by a subjective look at narcotic potential with various combinations of lung volumes and diving depths and, without the compounding and variable effect of exercise. We controlled the latter by using weights for descents and a modified, variable/ high-speed electric DRUMS for ascents. We’d also hoped that, perhaps, we might be able to touch on the 200m milestone as I felt it was physically and mentally within reach for me. Alas this was not to be.

Due to university commitments I’d planned for a 10-day stretch in which to carry-out these dives, diving every day, once to twice a day, depending on the depth. Some were concerned for DCI but previous dives showed that with proper warm-up procedures, correct juggling of dive depths, ample surface intervals and a dose of in-water recompression using O2 at the end of each session it could be done safely. Paul Murray, dive supervisor, arrived in Walindi (New Britain), some 10 days before I did to set-up dive boats and overcome any potential and unforseen last minute problems.

By the time I arrived in Walindi, after almost 24 hours of travelling, things were in place and ready to go. The following day we began diving operations with an easy 100m or so…well it felt like that anyway. Day 2, 122m and then things started to go desperately wrong. Over the ensuing days, for one reason or another, various components of the electric DRUMS failed; meaning that dives could only be done with just the back-up security system (manual DRUMS). It was a disappointing moment as both Graham Simpson (the medical officer) and a film crew from the ABC’s Catalyst program were currently on their way over from Australia. Repeated efforts by Paul and the electronics engineer to resolve these problems proved helpful, but with only three days to spare, inconsistent seas, a still non-functional surface dive monitor and no possibility to get decent build-up depths it became clear that things were becoming somewhat unpredictable, desperate and potentially unsafe.

Paul approached me and voiced his concerns regarding his ability to ensure my complete security under the current circumstances. After a group deliberation including myself Graham and Paul it became evident that this would become a reckless, “fly by the seat of your pants” operation. The film crew was visibly disappointed and so to salvage what was left of the situation I suggested we make the most of the situation and shift attention over the remaining three days to some unassisted ‘exhale-and-sink’ dives since I hadn’t brought my monofin. Once again spirits were lifted and it was hoped that I would somehow be able to surpass the world mark of 61m. With three days to spare and no specific preparation I personally felt it was unrealistic! However…

We sheltered behind the reef in some 80m of water and after a few hours of delays, boat positioning and repositioning I was free to dive. Despite the tropical surrounds it was evident that being able to stay warm long enough to do allow myself an in-water warm-up would be difficult and a bit of a hit-and-miss affair. The first of these days proved relatively effortless. On the first of these days, I resurfaced after a 43m dive with no urge to breathe but, I did feel some muscular fatigue in my upper-body during the last 10m of my ascent. Indeed, some 10 or so seconds after surfacing I was panting like a dog! This came as no surprise as it was simply an unclamping of the peripheral circulation and the release of metabolic waste products into the general circulation. By day two I decided to step it up to 50m or so. My technique, admittedly, was a bit rough but I felt, based on my previous diving trails in the pool and buoyancy differences aside, I probably had enough to manage, a ‘hard’, +65m. Anyway, after some delays in setting-up and difficulties with shivering on the surface before my dive I reached 52m with plenty of energy to spare but the muscles more fatigued than the previous day. The cold was running havoc with my ability to equalize my ears as I was losing control of my Eustachian tubes.

The last day. Mistiming my equalization I aborted at 15m. This forced me to resurface and regroup for another try, but the cold was difficult to handle and equalizing was proving ever more difficult now. Descending past 50m I release my nose-plug to no effect as my tubes sealed shut. At 57m I felt the ear squeeze and so tumble turned. Hovering for an instant, I looked down at the weight that signified 62m but I knew that this would be the extra 5m that broke the ‘camel’s back.’ I must have lingered too long or the cold had been too severe for me, as swimming up was like pulling my way through mud! I could feel the muscular effort and fatigue already setting in at 50m and it was a long climb to go yet. By the time I reached 15m and saw Dale, the security freediver I knew I had but a few strokes to go and I was still very lucid and in control but I suspect my technique must have been reduced to nothing as my arms felt like lead. Never out of breath but clearly very tired I felt relieved that we’d been able to salvage at least something out of a dire and desperate situation.

For those of you interested in some of my findings or wishing to know more about how to effectively use this diving strategy you can check my new (preliminary) website I constructed just recently at www.sebastienmurat.com

Sebastien Murat

I am certain that you will be able to overcome these unfortunate adversities you were presented with in Papua, on your next attempt.

There has been much discussion in this forum on "exhale and sink diving" and its potential benefits (on training mostly). As you are the pioneering ambassador of this discipline, a very big welcome to the forum, and to the invaluable knowlegde that you will no doubt contribute in the future.

Many successes for Team Amphibios and Safe Diving

"Indeed, some 10 or so seconds after surfacing I was panting like a dog!"...

i experienced something similar last summer when i was diving very heavily. i found that i would have no leg burn on the ascent. on reaching the surface i would initially have no urge real to breathe, then after a couple of seconds my legs would go on fire and i would become very breathless! i haven't experienced that (at least not to the same degree) since. i'm not sure why. it may have had something to do with a particularly strong blood shift i had during those dives... or perhaps due to the very steep thermocline (18C surface / 4C depth) near the surface.

Seb I was checking your website and noticed you are having a clinic out of Cairns.

Couple of questions

Will the boat be going out to the coral sea ie Holmes, or osprey or something.

Do you only teach exhale diving or will you teach full lung as well.


The panting was do to the stimulation of peripheral and chemreceptors by CO2 and H+, from muscle metabolism, re-entering the central circulation after the termination of apnea. This effect is much more pronounced when there is a strong vasoconstriction and the muscles predominatly switch over to anaerobiosis. If you hyperventilate excessively, on the other hand, the total CO2 store is much reduced and there is less heavy breathing. Also, because this results in a less vasoconstricted peripheral ciculation, the switch to anaerobiosis is postponed, lowering final H+ which consequently lowers rate/depth of breathing.

The trick is to get the right balance. The perfect balance occurs only when you've used up all your oxygen and are diving on a reserve. This occurs only on an exhale. Why and how?
Because the dive response stays fully manifest for longer during an exhale than an inhale. By that I'm referring to a more accentuated bronchoconstrictive dive response, which is prematurely terminated during inhale dives when the lungs re-expand (excessively) during the ascent (Bronchoconstriction can be so severe as to prevent any gas-exchange between dead space and alveoli). This premature termination of bronchoconstriction during inhale dives means that the dead space cannot supply enough oxygen to maintain consciousness for the duration of the ascent. Initially, when the airways become patent again oxygen moves from the dead space to the alveoli/circulation but this amount isn't enough to maintain consciousness for the entire ascent. On the other hand, a strong and more persisting bronchocostriction results in the dead space to become shut off from the central circulation until just the final stages of the ascent. There is in not in this instant a reversal in the o2 gradinet which would have oxygen moving from circulation to alveoli (as is commonly reported in the literature). Thus the oxygen stored in the dead space is able to adequately supply the central circulation for a bried period during the very final stages of the ascent, when hypoxia could be so severe as to result in a black-out. In essence, this mechanism is like being able to access a 'spare- air'/scuba tank when you need it most, ie., the final stage.

So how much oxygen can the dead space actually hold under these conditions and can it make that much of a difference?
Because of the steep pressure gradient in the first, say 10-15m, there is a rapid increase in the partial oxygen pressure early on in the dive. Bronchoconstriction/obstruction probably doesn't occur until sometime after residual volume is reached ~10-15m, depending on initial lung volume, etc. Despite the dead space's relatively small voume (~150ml) oxygen becomes rapidly concentrated in this space during the early pahse of the descent, anywhere from 300-400ml. This effect allows the dead space to increase it's oxygen reserve considerably more than it could otherwise. It stands to reason then that you might say then, that on an inhale this amount should be considerably extended since bronchoconstriction/obstruction happnes much later. This is so but there are some important differences: greatly re-expanding cause a premature termination of bronchoconstriction/obstruction and under severe exercise conditions this oxygen will be quickly used up, way before ever reaching the surface. Moreover, largely re-expanding lungs venous return.

The above is what I believe to be the 'secret' to proofing yourself against blackouts. Anyway, that's how I account for the level of uncomparable lucidity, but severe fatigue, I experience when diving to my limits. Take it, or leave it..........

Townsville, Aust.
Hi Ivan,

How's Wonga?
Caught up with Jim Freidlander (spelling!?)?

The clinics will only involve inhale dives in a comparative capacity to exhale dives, i.e., try one, then try the other and notice the effects.

At this stage it's likely that the trips will be on the outer Barrier Reef (50-60m depths) as I suspect few if any 'guns' will be able to d pick this up fast enough over 3 days to go beyond 30-40m on exhales...but you never know! Depending on interest, I may extend trip durations over a few more days and go out to the Coral Sea (Holmes). Certainly the visibility ou there (+60m on some days) woud make it well worth while. Indeed, I may well attempt a deepy after Greece and this would be a good opportunity.

Thanks Sebastien for your post. We know you are more private than most and I'm sure we all respect that, so it's nice to see a report on your progress and attempts.
Best of luck,
Erik Y.
Very interesting reading! A big thanks to Sebastien.

I was just wondering about something. I have watched some seals dive. And it seem they don't dive on a forcefull exhale, but more like a natural relaxed exhale?

So what is more safe a forcefull exhale? Or a normal exhale leaving about 1.5-2 litres of air (for me) left in the lungs?
Well anyways my experience with exhale/inhale dives on a mental level is that it seems that on a full inhale my brain thinks I have plenty of oxygen on my ascent with the expanding loungs, wich is not allways the case. And therfore it sends blood into my legs making them feel ok (less acid feel). But the fact is that I can feel it going from my head forcing me to use muscle contractions to keep the blood to my brain and not blacking out.

On exhale dives it allmost seem as the brain knows there is no air, so it now works with what is stored in the body. Also it seems to shift into alternative "Fuel" such as an adrenaline type of energy. This time on my ascent it feels like the brain is much more aware of what is going on. And keeps the air at the brain and everything else is beeing carefully transported to the areas that specifically needs it.

Well now I need to find my chemistry book and carefully read the text Sebastien wrote again to fully comprehend it.
Yes, they don't do forceful exhales...that would be taxing and an over-kill. The exhale is just passive.

One of the problems with inhales is that often the heart rate increase again during the the ascent. If the heart rate increases the dive response eases off and the peripheral circulation becomes once again active. This does not seem to occur to the same extent on exhales. Indeed, on some particularly 'stressful' dives heart rate can remain low and even continue to decrease.

As you mentioned seal, the adrenals do kick-in a little more which has the effect of further constricting blood vessels and sparing any remaining oxygen for the heart-brain axis; adrenaline also makes you more alert.

My experiences of exhale-and-sink diving is that it is everything I hoped diving could be and more. If I'd kept on going at the rate I'm going with exhales, I'd be dead and gone long ago.

By the way, I neglected to mention that for those whom aren't interested in clinics this summer there are opportunities for small groups of divers that would rather attempt personal bests, records or just hang-out picking-up info in Greece, Hawaii, Japan and Australia; using the DRUMS system. This service allows freedivers to dive in security at any time of the day, at short notice, as often as they wish (provided basic safety guidlines are implemented), to any depth and in any constant-weight discipline. The advantage is that we can process many divers, rapidly. You can find out more in a day or two on my website. This being an Olympic year with all eyes focused on Greece, this is a once in a lifetime opportunity for those wishing to promote freediving and themselves, if they so wish.

Sebastien Murat

Seb Im actually in Tasmania at Uni at the moment but will be back in Wonga for a month during June then again for 3 months over the Christmas break. I just missed Jim this year when I came to Tassie.

I think a lot of people would be interested to attempt personal bests in safety, I know thats what I and others have been waiting for. I can think Of a couple of guys from up at the wonga area who would be keen to come out and do some pb's with safety.

Hi Ivan,

How's exam stress?

Thanks for your interest.
As the website is rapidly being constructed you may want to keep abreast of the latest developments: Pool Clinics will also be happening in both Aust and Oz.

Otherwise I may drop in to say hello in Hobart as I'm due to visit with Micki in late October.


i noticed you've scrapped the clinics for Sharm. are there likely to be any other changes to the schedule? i would really like to attend a clinic - it will have to be either Monaco or Santorini now. need to check flights etc...

Our first exam is this coming tuesday for maths :head I suck badly at maths :D

What will you be doing in Hobart I guess not diving :hmm Water down there at the moment is getting close to 10C :(


Last minute decisions as July was always likely to be a contentious one.

However, that's it: no more changes. I hope you'll join me in Santorini. Should be a hoot!

Whjat only 10 degrees..! At this rate you'll have to take up skiing or climbing or something.

Micki's doing her doctorate in marine bio and one of her supervisors is down there. I'm hoping to hook up with the marine mammal unit and look through all their gizmos.

My wife Fiona did some of her PhD studies at UTAS, and I joined her for some of her time there. Tasmania is a great place - some of the best diving I have done was there. If you get the chance, go to eaglehawkneck and go and dive to see some seadragons.

Ben I have been down to eaglehawk neck, in fact we did a trip around almost all of Tassie. Didn't dive eagle hawk neck though. Did manage to go camping with a mate down at Scotts point South of Hobart. Monster abalone :p
My favourite dive was at a remote place called mussleroe bay on the north east coast, very clear water, big abs and fish.

I have seen one sea dragon up here whilst diving in the tamar river it was under a jetty, very cool indeed.

Jetty on the Tamar? We did a night dive at a jetty on the Tamar, only to about 8m, but it was nice. It was on the west side of the river, about 10-20 miles north of Launceston.

The coolest dive site we went to was near yours - south croppies point (ironically on the north coast). Fi and I were passed by a pod of dolphins. That's the only time I've seen dolphins whilst underwater.

Didn't dive south of Hobart though. I found the estuarine conditions there no way near as good as North/East coast.

Bicheno was nice too.

Abalones - I loved catching them - in the right place of course where they aren't all undersized due to commerical divers.

Ahh.....fond memories...Fi and I still have a vague desire about moving over there one day (permanently).

Yeah was the place of the jetty called Kelso. The area you described sounds like Kelso. A mate and I swim out off there a bit, the water is just over 20m deep only 50 odd metres from shore.

Yep dived Bicheno very nice clear water. Your right the water south of Hobart was much murkier than east coast however my mate is a local there and showed us this sick 4WD track that is very remote and unkown and it ended up being sick for abalone,

The only problem with Tassie is that Im always worried about Great whites, I never feel relaxed in the water :( Would you be moving to Tassie, brrr to cold. Have you been to Nth qld thats where im from water is much warmer, get to dive on the barrier reef etc.

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