BCD Failure

[wetb4igetinthewater]

I think you're underestimating how much of a buoyancy swing your lungs produce. Most people do.

It was a eureka moment when I could descend from the surface of the pool to the bottom and return using only my lungs. I had read @The Chairman talk about it, so when I worked on weighting myself to do that, I was amazed.

 

[wnissen]

The bottom line (no pun intended) is that if you do a weight check at the start of the dive, you won't be super negative.

No one is saying "don't dump weights", they are saying "with proper weighting you would not need to dump weights in this situation". Ditchable weight is there for a reason, and should be ditched if you've got any question about your ability to maintain buoyancy. But at half a tank and weighting that's in the general ballpark of correct, ideally the diver is positive with a full breath. Yes, that's ideal. There could be big swells, there could be no hard bottom, you could be tired or in distress, there are a million reasons why the ideal isn't happening. When in doubt, dump! But proper weighting can avoid getting into a situation where you are significantly negative in the first place. A pound of prevention is worth 10 pounds of cure.

 

[Member002]

It was a eureka moment when I could descend from the surface of the pool to the bottom and return using only my lungs. I had read @The Chairman talk about it, so when I worked on weighting myself to do that, I was amazed.

For me it was the first time I checked my weights after learning to do so during a safety stop.

I handed over some weight, exhaled, and started to fall. Then I took a deep breath, and started to rise. At this point I thought "Oh, good, I'm weighted properly".

Then I handed over more weight, and I could still rise and fall with just my lungs.

Eventually, as I got dialed in and added/removed small increments of weight, I found the minimum weight that let me breath comfortably without a runaway in either direction. But I won't forget how shocked I was that my lungs could shift so much weight.

 

[johndiver999]

It was a eureka moment when I could descend from the surface of the pool to the bottom and return using only my lungs. I had read @The Chairman talk about it, so when I worked on weighting myself to do that, I was amazed.

I think it is interesting and surprising as well. However, the relevance of this phenomenon to the incident that was being described by the OP seems weak.

I formulate this opinion based on two primary facts. One is that a diver who is suddenly presented with a catastrophic failure of their buoyancy control system, is quite likely going to be stressed. If a scuba diver is stressed significantly it seems unreasonable to assume that they can suspend normal respiratory function and instead, voluntarily breathe in an extremely inefficient and unnatural manner while the diver presumably would continue to actively kick in order to maintain their head above the waves. The diver would be required to not only support themselves at the surface but also to swim horizontally toward the boat at the surface in the "real scenario".

The other reason is that the scenario described by the OP with very rough conditions and a diver behind the boat, is COMPLETELY different than what is shown in that demo video of a dive in pool like conditions. BTW did anyone else notice how he made use of the ascent line as a "crutch" during his demonstration? LOL

So both the environmental conditions and the mind set of the diver are completely different between the actual scenario and the "make-believe one".

I could also question the viability of the lung volume manipulation solution to a real emergency from another perspective as well.

When people describe an out of gas situation (on the bottom), the general consensus seems to be that we should conservatively assume a DOUBLING of the air consumption rate. This assumption of doubling of SAC is purported to be applicable regardless of whether a diver is using a pony bottle or sharing air from a safe second on a buddy's tank. I'm not arguing that this is an inappropriate assumption for most recreational divers, but rather that it is a commonly accepted one.

However, it seems terribly inconsistent to assume that (on one hand) a diver is unable to maintain a normal respiratory demand while ascending with a pony bottle (and in fact REQUIRES double the air) and on the other hand, assume that a diver who has experienced a catastrophic BC failure, is going to be able to kick up and support themselves on the surface with a VERY inefficient breathing pattern that is clearly much worse than normal. So in other words, in one scenario we assume the diver will perform much, much worse than normal and in the other we are assuming the diver will perform much, much "better" than normal.

So playing with your lung volume on ascent and breathing inefficiently when completely calm and in benign conditions, is a neat demonstration of (rudimentary) diving skills, it probably should not be thought of as a reliable emergency protocol when the SHTF in bad conditions (for most recreational divers).

 

[Member002]

@johndiver999 I'm not sure how your criticisms of the video hold up. Pool like conditions is appropriate for demonstrating proper weighting. Rougher waters don't magically change how buoyancy works. If you're overweighted in pool like conditions your overweighted in rough waters, too. As far as the "crutch", he wasn't holding the line, just next to it. Since this was a video about buoyancy and weighting, and not "how to ascend in blue water without a reference", I'm not sure how ascending next to a line is relevant.

All that said, I think you're confusing "Can float with a full lungs" as meaning "Sink like a rock with normal/panic breathing".

That's not the case. At no point can you suddenly become a rock without your BCD if you're weighted properly (assuming rec equipment). Even in the video he shows that at low lung volume it's only a slight, slow descent, easily overcome with gentle kicking. In my own tests I found even horizontal swimming was still easy with some posture and trim changes.

Worst case scenario of full tanks and broken BCD I can "float" with a full lung, sure. But also, I can breath normally, or even fully exhale, and still stay at the surface with some light kicking. The same goes for at depth with wetsuit compression. The concept of quickly sinking to 30ft with a broken BCD is nuts to me. The diver was almost guaranteed to have been well overweighed if he was rapidly sinking from the surface to 30 ft.

I'm always curious when people argue about this if they've actually tried any of this. I dive solo a lot, and am pretty careful about checking all of my assumptions about self-rescue with actual in water tests and checks with my configuration. My experience lines up with the linked video pretty closely.

I would never argue someone shouldn't carry ditchable weight. It can certainly be convenient at the surface. My only arguement is that, in most common configurations, it's not necessary to dive safely.

How this relates to the OP is that, in general, if ditching weight was "needed", instead of "made my situation slightly more comfortable", that generally indicates being overweighted.

 

[hawkdoc60]

I recently bought an older Sea Quest BCD that never saw water. Before using it, I had it inspected. I got it back from the LDS with a clean bill of health. My first dive with it, it inflated nicely and did its job, but as I floated on the surface, I could hear the air hissing out of my shoulder dump. It was not overfilled, just leaked. I finished that dive and took it back to the LDS. Of course that time, they said the valve needed parts. It is now fixed correctly and no longer leaking. It just goes to show that the LDS can make mistakes when servicing the equipment.

 

[sabbe]

My wife had a similar situation first dive after having her BCD serviced. Coming up from diving the Lady Luck in Florida the whole power inflator and deflector assembly came off. Probably a little easier to handle as it'll hold air as long as you're horizontal and keep the hose down.

We covered this in the equipment techniques class last weekend. Always perform an inspection after having gear serviced.

 

[SlugLife]

I didn't suggest that at all. If the diver was wearing 5 lbs more lead than they need, is for the most part, irrelevant to the situation.

I think it is interesting and surprising as well. However, the relevance of this phenomenon to the incident that was being described by the OP seems weak.

I think we're mostly on the same page that both (1) dropping weights was the right call and (2) the diver may have been overweighted.

Unfortunately, your "if" above is incorrect, making the overweighting discussion very relevant. From the original story: "He didn't realize what had happened and kept sinking despite repeatedly inflating his BCD and finning. After dropping 30ft, he dropped his weights and surfaced." If the diver was appropriately weighted (or even 5-lbs over), he wouldn't have dropped 30ft despite kicking at the end of a dive. I'm not ignoring the rough-seas part.

The overweighting contributed to the incident, and was a potential danger to the diver. Dropping from the surface despite kicking is unsafe. Thankfully, the diver only dropped 30ft, but that could have been pretty dangerous if he dropped further, or experienced a 3rd problem at the same time (ex: ran out of air). Most incidents become accidents, when a bunch of individually fixable problems happen to stack up at the same time.

Both can be true:

• Ditchable weights may save you from a bad situation becoming worse.
• Being appropriately weighted may save you from a bad situation becoming worse.

The discussion of appropriate weighting is absolutely on-topic and relevant to the incident.

The discussion becomes more nuanced, when a divers advance, "master" bouyancy and additional skills, have a DSMB, and more .... but that discussion is where I would risk being off-topic and irrelevant to the situation.

 

[SlugLife]

The other reason is that the scenario described by the OP with very rough conditions and a diver behind the boat, is COMPLETELY different than what is shown in that demo video of a dive in pool like conditions. BTW did anyone else notice how he made use of the ascent line as a "crutch" during his demonstration? LOL

Are we talking about the same video? And the demo at 4m30s?


I don't see how it's a "crutch" or what is "lol" about that. He's not pulling himself up the line, nor do I see how the line is giving him any assistance with buoyancy. He has other videos on his site, where he does the same demo in sidemount gear with no control line nearby. So even if we pretend that control-line is providing magical bouyancy somehow, that doesn't undermine the point.

After watching his demo, I wanted to verify it for myself first-hand. Afterall, differences in equipment can affect bouyancy significantly and it's potentially unsafe if for some strange reason it worked for that instructor, but doesn't work for me. My own attempt was at 60ft, with about 2200 psi, a 5mm wetsuit, steel backplate, and about 2lbs over "ideal" weight. I had no problems ascending with an empty BCD & high lung capacity.

 

[wnissen]

is that a diver who is suddenly presented with a catastrophic failure of their buoyancy control system, is quite likely going to be stressed. If a scuba diver is stressed significantly it seems unreasonable to assume that they can suspend normal respiratory function and instead, voluntarily breathe in an extremely inefficient and unnatural manner while the diver presumably would continue to actively kick in order to maintain their head above the waves. The diver would be required to not only support themselves at the surface but also to swim horizontally toward the boat at the surface in the "real scenario".

When I get stressed my instinct is to breathe shallowly (but rapidly) at the top of my lungs. A stressed diver is a buoyant diver. It takes thought and control to keep breathing deeply in the middle of an incident. But I do agree that swell can make things much worse than a pool. When you're swimming into swells that are breaking over your head (even with an inflated BCD) the snorkel suddenly seems important!