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Depth simulation in a pool

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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The boys are back in town
Jul 11, 2004
Im headin back to school in jan, and am far from any deep water. I havent trained in about 6 months so my lungs are not what htey were then. I am going to use the pool at school to do training for apnea but i know that the deeper you go, the harder things are. I was wondering if there are any techniques that could somehow give me the same effect as simply diving deep, but in a pool of around 12ft deep?
You can do partial or full exhale dives to simulate equalising at depth. I fully caution against it though as it is easy to hurt your ears. Very easy.
Dont get in that pool and hold your breath without your buddy.

Like skindiver said, it's easy to hurt your ears. The pressure change is very rapid in shallow water and with empty lungs, you might not be able to equalize at all, while sinking like a stone.

Then again, in addition to being a good detph training simulation, it is a great way to practice your equalization. Just be careful and always have a buddy.

When I first started exhale dives in the pool, I'd get very uncomfortable and I know some people get to a point of almost panic. So start slow and careful. With full exhale+negative packing I found it impossible to equalize at first, but after half a year or so of playing around I learned to do a frenzel with filling my mouth on the surface and now those dives (4m) are quite comfortable even with full negative packing.

Just some rough calculations:
If you have lung volume of 6L, at 10m that would be 3L and at 30m 1.5L
So if you start with 2.1 litres (pretty much full exhale) at 4m (1.4bar), that would equal 1.5L = 30m. With negative packing you can go alot "deeper" still.

So very effective, but also very easy to hurt your self. Not only ears, but lung squeeze is a danger too. With negative packing you might be reaching lung volumes that equal 50+ metres in a matter of seconds, while in a normal dive that would take at least 1 minute or more. So the stress on your lungs is much higher. Start with moderate amount of exhale and increase it as you feel totally comfortable with the previous. Learn to relax and enjoy the feeling on the bottom, only then move to the next stage. At no point should you feel pain and if you happen to cough blood, stop immediately. You cannot rush this one, it's not one of those "no pain no gain" types of exercises. If you try to rush it, you'll just end up with injured lungs...

Once more: always with a buddy! (like all diving should be, but especially here)
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nice.. i had no idea that even had reverse packing. wow. Is that as it sounds? just the exact opposite of regular?

oh..and unfortunately i found out that my buddy wont be there this semester...terribly upsetting, so unless i find a new one i wont be doing anything close to limits. Do you think, say, goin at 50% would be of much use? and if so would it still be dangerous? i know you should ALWAYS have someone there, im just curious as too if that level of training still poses the same risks?
Simply don't do it. No one can estimate for you nor can you estimate what a 50% training level is.

I’m sure Skin is right. Not to do it without a partner is the best, but I think reverse packing dives to stimulate equalization is one of the more safe things a person can do in pool training by themselves. That is if its done quickly..

About the max of the apnea is only about 20 seconds. Most people’s SaO2 should be way above blackout range just with the O2 stores in the blood and tissue. Breathup on the surface, exhale, reverse pack a few times, and dive and try to equalize, then come back to the surface and breath. Adjust the number of reverse packs based on your success of equalizing.

At the PFD clinic Kirk warned people not to stay at the bottom of the pool doing negatives for long, because it can cause plasma (or what ever the scientists and doctors want to call it) to come into the lungs, just like when doing an extremely deep dive. This is harmless, but it will decrease the lung volume and efficiency until it is absorbed back into the blood stream in about 24 hours. The result will be a decrease in the effectiveness of your pool session for that day.

Martin Stepanek said he is big believer in doing negatives for bringing on the dive reflex. I think both equalization technique and dive reflex can be done quickly with minimum danger of passing out.
Just my opinion,
I do negatives to start both pool and open water sessions. Helps a lot in speeding up the diving reflex. Like Don says, do short negatives and don't stay on the bottom long. I have found that doing full exhales and lots of reverse packs can get my lung volume so low that I almost can't clear at 4 meters. That probably simulates the depth/preasure effect of more than 40 meters, maybe a lot more. This has helped greatly my ability to clear at depth in the ocean. However, if I do very much of it or stay on the bottom more than a few seconds, I end up with lung discomfort that lasts for weeks. Feels like a residual chest cold. So, try it, but be careful and go slow.

I have done 60m + training dives in cyprus and that was nothing compared to the day i tried doing negatives in a 5m pool. I nearly drowned, breathed in water and stuffed up my ears for two months so badly i couldnt even play hockey without pain... and i took it easy. There is little point lying on the bottom if you are doing deep equalising simulations.
You are heavy on the way down, quite breathless most of the time, and trying to blow the little remaining air into your ears as you go drop deeper. When you start back heavy and with empty lungs, a need to breathe for me is much more pervasive than on a real deep dive and one can easily snort mask water in by way of contrations when negative.

Obviously this is not my thing as i equalise at 60m the same way and as easily as at 3m. But it may well be good for others. Do it if it turns you on but not alone.

Skindiver said:
I have done 60m + training dives in cyprus and that was nothing compared to the day i tried doing negatives in a 5m pool. I nearly drowned, breathed in water and stuffed up my ears for two months so badly i couldnt even play hockey without pain... and i took it easy.
I find it impossible to do negatives for similar reasons. The urge to breathe is incredibly strong and uncontrollable, much worse than a max static. It is the only kind of training which I totally refuse to do.

None of the other freedivers I train with find it as hard as I do, so I don't think it is a bad idea for everyone, just that it doesn't suit me.

Skin, you've got my attention. Why is your experiance so diffent from mine????? How do you clear? When you were doing negatives, where you reverse packing? If so, how much? Have you tried this more than once? Is it possible that you can exhale to a much smaller residual volume than I can, could that be the explanation?
My negatives include 5 purge breaths, about 20 seconds of full exhale, more to reverse pack(I don't get much air out when reverse packing), and a dive of not more than 30 seconds total time. I skul with my hands to slow down in the last 2 meters. I clear very fast, hands free, no mouthfill. If I reverse pack a lot, I need to valsalva at the bottom. Urge to breathe is pretty strong on number one, but after I've done 3 or 4 there is no urge to breath at all.

What's different? Is this just individual variation? I'm petty sure 60 m in the ocean is way beyond my ability.

Sure is a good warning to taking such things slowly.

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Hi Connor.

Perhaps Im just not crazy about being out of air much. I prefer to style my diving so that i'm in air all the time or reduce the urge to breathe significantly. I have big lungs and i breath up agressively, work relatively hard to build CO2 and save O2 on the last part of my dives and keep my dive times relatively short.
A long ocean dive for me is two minutes and even then i'm intentionally pushing myself to get to two minutes. I was doing 60m training dives in Cyprus in less than 1 min 30 sec. Slow down 1 min and fast up 30 sec. I figured that if i moved it, i could beat running out of air. I never felt an urge to breathe on any of these dives. I trained for this in gym strengthening my legs for the uphill shunt. It worked well for me. I surfaced with plenty air. Just tired from the sprint.

For the negatives i would simply blow out completely even bending at the waist to exhale fully. No negative packing. As i bend to duck, I force up a mouthfill and challenge myself to equalise with that to the bottom of the 5m pool. I could, but if an ear stuck i still sank so fast that by the time i got it right it was too late. It never hurt a bit, but the next morning my my ear was blocked with swelling and fluid and it took months to come right.

IMHO These are advanced training techniques for advanced divers who have identified a real need to train for the purpose of overcoming a realised equalising difficulty. I would suggest doing them only while descending on a weighted and tied off line to control descent speed.

As for 60m being beyond anyones capabiities, this is not true. You will dive as deep as you really "want" to dive, as deep as you are willing to push your mind to accept.
There are some technicalities you need to overcome approaching 50m but after that IMHO its just mental strength and more of the same. Having said this i can only speak for myself and up to 60 odd m. Beyond that i have no room to talk.

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I find the speed of decent in negative pool dives a problem too. Since pressure increases so quickly in the first 15’ feet, you really have to slow down the descent, to simulate deep diving equalization. With almost no air in your lungs the decrease in buoyancy compounds the decent speed. With a 1.5mm suit, I take off all my weight and barely have to kick to make it to the bottom. Without a suit I sink without any fining.

I also made up a buoy with a rubber-coated anchor for the pool. I have mainly used it to help people learn to equalize, but I am going to try it for my own negative dives too.
Thanks for the reply Skin. You give me hope of "diving my age" as Bill laid on us. That would be 55 m and I'm not quite past 40 m yet, but getting deeper every summer. Your profile of slow down, fast up seems like my kind of strategy, but 30 seconds up out of 60 m is really moving. That is pretty close to my flat out sprint speed. I will play with that idea come summer diving season.

Back to the point of the thread, it is pretty clear that this technique requires a great deal of caution. Some divers have trouble with it and some don't. A diver trying the technique for the first time doesn't have any idea how his body will react.

wow, 60 meters in a minute thirty is damn fast. I have a hard time keeping up with a 1m/second rate up and down. My last free immersion dive to 30 meters took me 1:51, but i was stopping because of equalization problems. Still though, i think you might have a little more depth in you if you slowed your ascent, because you wouldnt burn up oxygen at such a fast rate. I could be wrong though, you know better then me what works for you:)
Having just spent an hour doing mostly negative pressure dives in a pool, I'm finding this thread very interesting. Like most of you have noticed in yourselves, I have a very strong urge to breathe on my first couple of dives. After that, I can reverse pack till I only have enough air to equalize twice, and still feel comfortable at 5m for about 1:30 or so. My longest dive after reverse packing was 2:15. I also feel definate pressure on my chest when I do these dives.

My reasoning for doing alot of negative pressure dives is to build flexibility. I got squeezed twice in '04, and both times were at a depth much shallower than my pb. So now I strech, and then spend as much time as I can on the bottom of the pool with my lungs as empty as I can to get the max pressure effect. And when open water diving, I dive on passive exhale as deep as I'm able to equalize. So far I can only make about 13m, but divers much better than me say that once I master the mouthfill equalizing, I should be able to hit 30m on an exhale! I don't know if I'll ever get that far, but it is a truly relaxing and comfortable way to dive after the first one or two. I've seen my lowest heartrates on exhale dives (~25bpm). And I seem to always feel more relaxed after a session of empty lung diving as opposed to diving with full lungs and packing. Incidentally I don't pack anymore during depth training.

My $0.02 :D
What's up with the dead thread revival thing? How are you even finding these?
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