Discussion of best practices for advancing in cave diving (moved from A&I JB thread)

[ginti]

whether its thirds or halves the same applies you cant share easily with one hose and you still have the reserve on your back if its thirds or halves -the only advantage for halves I can see is the efficiency of gas transportation. The upside of thirds is presumably your stages are closer together so you have less distance to cover a meltdown and you always closer to new gas

Not really. Let me give an example.
BM 12l twins at 170 bar, one stage S80 (slightly less than 12l) at 200 bar, rule of thirds; the calculation is the following:
(1) calculate the gas you need in case the S80 fails; in the worst case, (S80 fails when you pick it up on the way back), you need 12l*100bar=1200l
(2) subtract from the gas in the back-mounted cylinders the gas calculated in point (1): (170*12-1200)/12=120 bar; this is the gas you can use for calculation.
(3) calculate the rule of thirds with the remaining gas calculated in point 2: (170-50)/3=40bar
now you have half the stage + 40 bar of the back gas to go inside the cave and the rest to solve problems and to come back.

With this type of calculation, if you need to share gas, you always share the back gas - that is, you have two hoses to share. Also, you have enough gas in case of one-stage failure to share (the 50 bar of point 1), + the reserve from the rule of thirds (40 bar in this example).

Adjust calculation if you want to be more conservative (I usually breathe slightly less than half a stage, just in case I am more stressed for whatever problem when I come back)

EDIT: the numbers are just examples to make the calculation understandable; usually, I start a dive with anything between 200 and 220 bar in the twins, and between 190 and 200 bars in the S80, depending on how much the station filled them.

 

[Germie]

Cave diving is, IMO, something that should never be rushed. I look at diving like a chain: the first link is your OW and the last link is where you want to end up (say, for example, cave CCR). Each link after and preceding are necessary. If you rush, or cut corners, you end up with weak links or a broken chain. Once you are proficient and comfortable, you move to the next link in the chain. I personally came to this conclusion a while back when I realized I was moving too fast and needed to slow down. Too many people around me were already moving to DPV and CCR and I succumbed to the pressure. Ultimately, I sold my CCR and took a pause on DPV. Absolutely nothing wrong with going slow and being safe.

I agree. But, then another question is, what is rushing? The answer is quite hard I think.
Here in Europe, you see that almost every intro to cave diver or C1 diver goes over certification limits within 5-10 dives after they got their certification. The first rule that is 'broken' is the gas rule, they start doing dives on 1/3. The second rule they 'break', is to take a stage with them. And then also they start doing jumps.

So is the problem then the too limited first cave cert? Or are divers rushing too fast? And if they can do the complete full cave course in 1 week, is that rushing?
I think if a diver is ready, they can do the complete course. This is also a phylosophical thing, you 'are allowed' to do 'all', but you don't have to. So then people have learned more about things, how to use a stage (a lot think 1/3 also must be used from every stage), limits of 1/3 rule, etc. And then you see them doing 'normal' things very within the limits of their full cave cert.
But of course, not every diver is ready. And it is hard sometimes to really see everything. I always do a 'let's meet each other and let's know each other' dive before I say yes. But that is not possible with every instructor. Also you have divers that do a 'yes and Amen' course and then will do diving their own way.

I am also a person myself that did the full cave course in 1 week, in Thailand. On of the reasons was that I did not want to be 'limited'. I had had very serious discussions when I was quite a beginner in diving about the 2*/aow cert with a club that had no time to do it, and then did it with padi (I had 53 dives when finishing it, so not the minimum of only 9). The club started to complaign I was not ready, but the main reason was they did not have time. In that time I did 5 dives a week, sometimes more. Every evening I was diving, in weekends, I was diving. They only did maybe 1 dive a week or less. They also started to complaign when I decided to do my 3*/DM course PAID by myself somewhere else with 120 dives. That was also too fast.

So that makes for me always the question, what is too fast?
Do you count time? Do you count dives? Do you count different divesites? Do you count hours under water?
Most divers only look at time between a course. On internet you reed a lot about too fast when someone had certificate A only a few weeks or months before B. But a lot of details are not known. The amount of dives between are not known. The hours under water also not.
So can you say it is rushing or not if you don't know all details?

I read here about exhausting oc diving before moving to ccr. Yes, this was done 10-15 years ago. Most divers started oc and then some bought a ccr. I see a transition to buy quite fast a ccr now. 1 of the main reasons is the price of helium. If you want to go deeper than 40m, that is not nice anymore on oc and with the use of trimix.
You also see a reborn of deep air. Where 60m on air was notdone anymore, now you see it is coming back again.
Yes, I started ccr really because I was limited on oc. I have done 17 minutes at 110m on the HMS Russell wreck in Malta on oc (with safety divers), and then I thought now I want to have a ccr. I calculated the turnover time/price will take 8 years if I do 4 dives over 100m per year. And the unit will not get broken. The turnover never came, but I like diving ccr sometimes. In the first years I did 8-10 dives over 100m per year. Then it transitioned to ccr cave diving as main goal. Also a sidemount ccr came.
But I still believe in use what works and is needed for the job. I still dive oc backmount AND sidemount.
But now I see divers buying a ccr before they are finished with oc diving. So this means some experience under water has to be gained by just diving. This means probably that you have divers on a ccr course with less hours under water in total than 8 years ago.

BUT, a thing I see a lot around me and that is really important, that is the use of computers. How many divers are able to calculate things nowadays? That was 10 years ago a must to pass an exam. Now the computer does the job. And I think this is also part about going too far with too less bailout by a lot of divers or on on a dpv.

So in my eyes, it is still quite hard to tell exactly what zero to hero is. Or what too fast is. From a computer it is easy to write down. But in reality, it is quite hard to give a definition that fits for everybody. I see that some divers really can go faster than others. I also agree that most standards are too minimum for the average diver. But then it is the discretion or opinion of the instructor.
You cannot stop everybody, you only can advice.

Computers made diving safer, but also made divers lazy. And this is maybe the main problem when diving a ccr or dpv.

 

[Germie]

Not really. Let me give an example.
BM 12l at 170 bar, one stage S80 (slightly less than 12l) at 200 bar, rule of thirds; the calculation is the following:
(1) calculate the gas you need in case the S80 fails; in the worst case, (S80 fails when you pick it up on the way back), you need 12l*100bar=1200l
(2) subtract from the gas in the back-mounted cylinders the gas calculated in point (1): (170*12-1200)/12=120 bar; this is the gas you can use for calculation.
(3) calculate the rule of thirds with the remaining gas calculated in point 2: (170-50)/3=40bar
now you have half the stage + 40 bar of the back gas to go inside the cave and the rest to solve problems and to come back.

With this type of calculation, if you need to share gas, you always share the back gas - that is, you have two hoses to share. Also, you have enough gas in case of one-stage failure to share (the 50 bar of point 1), + the reserve from the rule of thirds (40 bar in this example).

Adjust calculation if you want to be more conservative (I usually breathe slightly less than half a stage, just in case I am more stressed for whatever problem when I come back)

Ask about how many divers is learned to use 1/3 on every cylinder, so also on stages. They don't understand some basic principles. But you see it around you.

 

[ginti]

Here in Europe, you see that almost every intro to cave diver or C1 diver goes over certification limits within 5-10 dives after they got their certification. The first rule that is 'broken' is the gas rule, they start doing dives on 1/3. The second rule they 'break', is to take a stage with them. And then also they start doing jumps.

Honestly, I don't know as many cave divers as you may know. But the few GUE C1 divers I know (around 20, although some are now C2) did not break any rule. We tend to be a pretty conservative community, and breaking standards would be a problem for us (most of us would not dive again with a buddy who broke a rule). But I agree that we feel the pressure to move on with training. After roughly 15 C1 dives, I felt the need to move on. After 30, I started feeling bored (I saw anything easily accessible and could not travel to America to see something new at that point). I mentioned this issue to some instructors, and apparently, there is no easy solution...

(By contrast, I did roughly 25 T1 dives at this point, and I don't feel the urgency to go deeper at all - although I am fascinated and will progress at a point in my life)

My (few) friends from other agencies don't break standards either (IANTD, TDI, FFESSM), but that might be because I bond with very conservative people. I only know one pretty aggressive guy (diving air at 70m inside a cave). But, again, my experience is limited...

Ask about how many divers is learned to use 1/3 on every cylinder, so also on stages. They don't understand some basic principles. But you see it around you.

That way is how I was taught. I admit I was curious about the methodology before doing the course because I could already see the issue of having our reserve in the stage (if it fails, it's lost, right? We cannot share it, and so many other problems), but did not have any solution yet.

But I honestly thought that was the standard in the industry...

 

[Wibble]

I agree. But, then another question is, what is rushing? The answer is quite hard I think.
Here in Europe, you see that almost every intro to cave diver or C1 diver goes over certification limits within 5-10 dives after they got their certification. The first rule that is 'broken' is the gas rule, they start doing dives on 1/3. The second rule they 'break', is to take a stage with them. And then also they start doing jumps.

So is the problem then the too limited first cave cert? Or are divers rushing too fast?

Isn't all "technical" diving like that? (Excluding basic diving)

When you get your first OC trimix, you start pushing the limits, such as more or less helium, decompression, more deco gas, solo diving. Normoxic gives you two deco stages; then you push the limits again maybe adding a bottom stage and longer dives, pushing the "keep at least 50% of your gas for your buddy".

Ditto CCR which really is a progression. Initially keep to simple dives but soon after you'll be adding decompression stops, two bailouts, diving alone...

Isn't this just learning and gaining experience as you go?

Same in caves (or mines for many of us in geologically challenged locations). Intro means no jumps, no restrictions, 1/6th gas. Effectively the length of your primary reel. However, as you progress and know the location, you will naturally start pushing things; a jump, another jump, circuits...

Pushing into a tight restriction on the other hand... It's bad enough when dry caving, but with all your diving kit... not particularly enticing!

 

[Vicko]

A person has to get experience somehow, we all were unprepared for a dive before we actually did it for the first time.


That said, and this is just a opinion that may be invalid, the proliferation of rebreathers has created a lot of woefully inadequate divers. A person with 20 hours on a unit can now attempt a dive that was impossible for some of the best divers 10-15 years ago and as long as their unit works he will succeed. If there are any problems the diver will become a statistic.

In Europe there have been a number of incidents where people who just did their cave ccr or even just mod 3 course got killed due to a very simple mistake while undergoing 3+ hour long complex dives.

 

[ginti]

Isn't all "technical" diving like that? (Excluding basic diving)

When you get your first OC trimix, you start pushing the limits, such as more or less helium, decompression, more deco gas, solo diving. Normoxic gives you two deco stages; then you push the limits again maybe adding a bottom stage and longer dives, pushing the "keep at least 50% of your gas for your buddy".

Not really, at least not for me. There are few easily accessible caves around, so most people always go to the same few places (in Europe, Lot, Sardinia, Spain, some mines in Germany and Belgium, and a few other spots) and get bored soon because they always see the same things.

With normoxic trimix, you can explore anywhere; tons of wrecks and naturalistic places are interesting in that range. It's a long time before getting bored and feeling the urgency to move to the next step (at least, it is for me and all of my friends... and @Germie agrees).

If you go diving for the technical challenge, that is another point... but this is a hazardous way to approach diving, in my humble opinion.

 

[Wibble]

Beyond initial training, for example MOD1 and ANDP, all "advanced" courses require you to have some experience to bring to the course?

Just for example, Solo Diver. This isn't really a course at all as you should possess all the skills required for the tests.

MOD2 needs you to be able to handle two bailout stages; to have excellent control; decompression stops, etc.

MOD3 takes it much further where you need experience with many bailout cylinders, etc.

Caving too where Full Cave would need you to be pretty handy with reels, tieoffs, jumps, line markers, using multiple spools/reels. All of that requires some experience in advance.


What I'm getting at is you sort of build your experience to the next level, then do the course to formalise it.

Along with your experience, you'll slowly gain more abilities to handle difficult conditions. Always remember one of Steve Davis' Speaking Sidemount podcasts where he interviewed an incredibly experienced cave diver who said he never stops learning and is doing dives now where he would have had problems in the past -- his experience then was very high, now it's well beyond most normal people!


TBH it's when problems happen that you really learn. Hopefully you didn't put yourself in an impossible position because of your existing experience.


Edit: the above isn't applicable to everyone. Some styles of "team" diving and training will progress more formally.

 

[ginti]

Beyond initial training, for example MOD1 and ANDP, all "advanced" courses require you to have some experience to bring to the course?

Just for example, Solo Diver. This isn't really a course at all as you should possess all the skills required for the tests.

MOD2 needs you to be able to handle two bailout stages; to have excellent control; decompression stops, etc.

MOD3 takes it much further where you need experience with many bailout cylinders, etc.

Caving too where Full Cave would need you to be pretty handy with reels, tieoffs, jumps, line markers, using multiple spools/reels. All of that requires some experience in advance.

With GUE, what you wrote here is not valid. When you do a Cave 2 course, you don't need to be pretty handy with jumps, line markers, and using multiple spools/reels. You just need to be pretty handy with Cave 1 skills - namely, reels, tie-offs, fundamental skills, etc. A more exhaustive list is here.

The same for Cave1, Tech1, and DPV classes - you just need to be solid with the previous level. I don't know about other courses, but I assume the situation is the same.

I cannot speak for agencies other than GUE, but I hope the situation is the same.

For example, I heard that, with the UK CDG, you constantly work with a mentor, so, again, there is no unsupervised learning.

What I'm getting at is you sort of build your experience to the next level, then do the course to formalise it.

As I have just mentioned, no, this is not how it works with GUE, and honestly, I am totally against such an approach. It's just risky, the best way to have accidents.

You first try something new with an instructor with enough experience, and then you practice.

 

[Celt]

Now this is moved from A&I it’s fairly safe to say people coming out of cave and wreck courses are just about qualified to put their heads in the entrance of a new wreck or cave. There’s divers in tourist wrecks and caves who couldn’t crawl out from under their own bed. It’s basic physics , if you can’t do it on dry land or cave, without diving gear, you’re not going to do in water.