2nd-stage swivel failure in Cenote Cristalino, Mexico - 06-Nov-2010

[CaveBuddy95]

Great you came out unhurt.

Things to bare in mind are the fact that, at all time, you should know what reg you are breathing from. Sidemount is different from BM, as you know and it is essential to know what reg is in your mouth. Having said that, we all went through this drill during cave class. Having the instructor sneak from bellow and purge any reg reg to see if you are 'aware' of what is your breathing source. Be it in basic sidemount or basic backmount, it is fundamental skill.
Basic sidemount regs/house should be set exactly the same as basic backmount. One short bungeed (with 90°elbow - not swivel) and a 7ft. This works great. And on top of that, it makes transition from backmounted doubles to sidemount configuration, a breeze. And it works great until you reach 'real' sidemount cave passage. On top of that, sm short hoses are not that easier to dive with. There are pros and cons.
In a 2 man team, if using sidemount at a basic level, both need to have same regulator configuration, in this case, I suggest basic sidemount reg config. But what do I know really!!
Sharing air on long hose is in muscle memory, peace of cake whereas passing over a cylinder needs preparation and practice. If tank is not rigged adequately and the protocol is not reharsed it can lead to disaster or at least not such uneventful exit.
In real sidemount cave it's different. I presume or wrongly assume you were not in SM cave.
Sidemount is old practice and is under estimated and wrongly seen as some way to sling 2 tanks on our sides and go on but there is more to it than that, specially in cave environment.
Training is important at that level of advanced diving. The value behind good training is that it will give you the right tools from the get go as well as make you aware of others gear configuration - what to do or what not to do.
I just took sidemount cave trianing with Steve Bogaerts and after 50 dives in SM on self-taught rig config. I just got my eyes opened to real sidemount caved diving. Yes, there is huge value in taking training from a guy like Steve Bogaerts. During class we reached the limits of the long-hose use, that is, the cave was getting small, not advanced small but small enough to demonstrate that long hose has its limits. Limits that I will reach after going through a good serie of basic sidemount cave dives and I will go to Steve again to take the advanced sidemount course.

Again, I'm glad you came out unhurt.

Cheers

ps:did I mention that swivels are dangerous? no? so better now that never! SWIVELS HAVE BEEN RECALLED FOR MONTHS NOW - 90° elbows are the future!

[whodunit68]

There was not a question in my mind about which reg I was breathing.
You are right, it was not a sidemount-only section of the cave.
Many valve shutdowns during full cave but also discussed were probabilities of the correct valve. The swivel is off to the right and gas exited to the right of that. I heard and felt bubbles on the right so I immediately shut off the right - exactly what I was taught, meanwhile switching to the other reg. If one of his regs or hoses fails, the distinct advantage is that each is very much on its respective side.
He likes the short hose and that's his perogotive and i will have to make my choice...

[CaveBuddy95]

There was not a question in my mind about which reg I was breathing.
You are right, it was not a sidemount-only section of the cave.
Many valve shutdowns during full cave but also discussed were probabilities of the correct valve. The swivel is off to the right and gas exited to the right of that. I heard and felt bubbles on the right so I immediately shut off the right - exactly what I was taught, meanwhile switching to the other reg. If one of his regs or hoses fails, the distinct advantage is that each is very much on its respective side.
He likes the short hose and that's his perogotive and i will have to make my choice...

No more comments

[Michael Stroeck]

So, a few hours later (I deliberately waited), I wonder some things...in my current sidemount configuration, I heard the free-flow on my right side. This could *easily* be confusing since the left bottle 2nd-stage swivel is on my right side and my long-hose 2nd-stage is on my right side. This was the first in the problems here. I switched off right because I heard it on right.

For humans, there is no such thing as directional hearing while underwater.

If you get the sensation that something is coming from the right, that might be true or not... But it won't be your ears telling you that. You hear mostly via bone conduction while immersed, and that just is no good for making out the direction of the sound source. You can not rely on hearing to locate a the area where you are losing gas.

If you can not see exactly where the bubbles are coming from is better to ignore your unreliable senses completely and just always methodically go through a well-defined procedure that will catch the offender at some point.

1) Have a pre-determined valve-shutdown procedure.
2) Perform it often and meticulously for training purposes.
3) Follow it to a T in any emergency situation until you can't hear bubbles and are breathing from something other than the shut-off regulator.
4) In stressful situations, do not even think about trying to make critical decisions before you have exhausted all the standard, well-ingrained reactions that you have built up in training.

Many valve shutdowns during full cave but also discussed were probabilities of the correct valve.

Probabilities are fine, as long as you use them to define your procedure which you then always use. I just think its not possible to make judgements based on probabilites while you are actually losing gas back in a cave. IMHO, the chances of messing up, getting even MORE freaked out and then drowning are much higher than making the right judgement.

[limeyx]

For humans, there is no such thing as directional hearing while underwater.

If you get the sensation that something is coming from the right, that might be true or not... But it won't be your ears telling you that. You hear mostly via bone conduction while immersed, and that just is no good for making out the direction of the sound source. You can not rely on hearing to locate a the area where you are losing gas.

If you can not see exactly where the bubbles are coming from is better to ignore your unreliable senses completely and just always methodically go through a well-defined procedure that will catch the offender at some point.

While you might be "technically" correct regarding the hearing (I don't know enough to say), in practice I (and others) don't find what you wrote here to be the case.

I have had many many cases in class where "surprise" bubbles are used to emulate a failure and in every single case, I was able to determine which "side" they were coming from (notwithstanding that bubbles on one side of the body can come from a regulator on the opposite side)

In our last class (CCR), i was also easily able to tell that the slight "clunk" was my left-side quick QC4 being unhooked by our instructor.

That said, in my classes there is a very simple and repeatable process for hunting down and fixing/handling leaks, and the first step for someone "helping" the victim is to make darned certain the regulator that person is (or is attempting to) breathe is fully turned on, regardless of where bubbles are or appear to be coming from.

Nick

[Michael Stroeck]

I have had many many cases in class where "surprise" bubbles are used to emulate a failure and in every single case, I was able to determine which "side" they were coming from (notwithstanding that bubbles on one side of the body can come from a regulator on the opposite side)

In our last class (CCR), i was also easily able to tell that the slight "clunk" was my left-side quick QC4 being unhooked by our instructor.

Hi Nick,

Definitely, you can also feel bubbles, or the act that causes them (unhooking). I was talking about the "hearing" part specifically. The real reason for my post was the "procedure" part, and what to do when you don't actually know what's going on.

[limeyx]

Hi Nick,

Definitely, you can also feel bubbles, or the act that causes them (unhooking). I was talking about the "hearing" part specifically. The real reason for my post was the "procedure" part, and what to do when you don't actually know what's going on.

I do agree for sure with the procedure part. Whether it's hearing, feeling or something else, so far I have found I can make a very good determination where to start looking for a leak (thankfully mostly in classes!)

[Bobby]

Glad that the dive came out OK for you. There are some things to take away from it, that is sure. The swivel issue was the main cause for the problem but I don't believe that it was the root cause.

I am not sure what or why others are teaching the way they are. I have always taught putting a person on my known source of gas before turning anything of theirs off. I have had a number of failures and had others in my team with failures in SM. The need to shut down someone elses cylinders in SM has also never been needed. With the OP's configuration I can see how the wrong cylinder was shut down. The response should have been to turn the shut down cylinder back on before shutting down the other one. Since his team member shut down his cylinder, the team member should have put him on his gas source first.

SM does not have one widely accepted gear configuration yet and may never have it due to the various specialty reasons for using SM. I believe this is a classic example of why people should spend time getting experience with doubles (BM) and honing thier muscle memory before moving to SM. For any advanced technical diving such as SM, CCR, multiple stages, etc. I approach my gear configuration with a solo menatality and the ability to lend assistance for another diver regardless of them being in my team or not. For me that means a long hose on every dive and configuration. I have not yet found cave small enough that I could get through but I could not get a cylinder through that has a long hose on it. If the passage is small enough that a long hose won't help someone then I won't dive it with a teammate that is not comfortable doing the passage solo. Gaining dive time and experience IMHO builds the knowledge on handling configurations, situations, etc..

Bobby

[Greenwood_60]

The bubbles are going to displace water as they move past you. There will be some distance from your body they can pass and you will still feel the movement of the water that they displace. The effects will be much greater an object passing you in air due to the incompressible medium, and the viscosity of the fluid.

The brain will combine cues from multiple senses. You will hear the bubbles, and feel the direction, and your brain will combine that in to a sense of bubbles in a particular direction.

[jcbrown]

For humans, there is no such thing as directional hearing while underwater.

If you only hear in one ear, you can have directional hearing. It is a learned skill.