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Two days in an underwater cave running out of oxygen

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Re: Two days in an underwater cave running out of oxygen

#231

Post by mulmen »

gpawl wrote: post #183
coleifer wrote: post #40

Earlier quoted context omitted.

I race motorcycles and also ride on the street most days, so this is a familiar topic of discussion with my wife, especially considering that we have a two-year-old son. What I can say on the subject is that there's a big difference between taking every precaution to minimize risk and being careless or reckless. What stood out to me when reading this article was "why the fuck would you use a guideline that could brea…

The day you flip out on your bike and land on your head, god forbid, the same questions will be asked of you.

That's not entirely fair. There's a wide range of motorcycle gear available. Buying the best stuff, the equivalent of high-strength line, does dramatically reduce your risk of injury or death relative to cheap or no gear. Asking if the line was the appropriate type is a valid question.

A huge part of riding a motorcycle is preparing for the unexpected. Always having an escape path, knowing your limits and the limits of your gear and riding within them. I'm sure there are similar concepts for divers, it's entirely fair to ask if this diver took all the necessary precautions or if there are additional precautions that are possible.

Re: Two days in an underwater cave running out of oxygen

#232

Post by mulmen »

huhtenberg wrote: post #92
dragonwriter wrote: post #74

Earlier quoted context omitted.

> I might be speaking out of line, but taking on these kinds of risks with young children at home seems kind of selfish. People die. A key responsibility of being a parent is to make sure arrangements are made for you children should you die. I suppose whether this risk is warranted involves some complex calculus taking, among it's many inputs, the quality of arrangements that the parent has made, the actual mathemat…

> A key responsibility of being a parent ... is to be there for your children.

At what cost? Should parents ride bicycles? Run marathons? Swim? Go outside? Where do you draw the line?

Re: Two days in an underwater cave running out of oxygen

#233

Post by mulmen »

ajross wrote: post #5
belovedeagle wrote: post #2

I wonder - did they take steps to replenish the cave's oxygen? If not, it's useless for the next person... I guess this is kind of silly and naive, but it's what I would do.

The air in the cave will come to equilibrium with the partial pressures of gasses in the water, which itself is in equilibrium with the atmosphere. It's not as closed as system as you think, even though it probably wouldn't outgas oxygen as fast as the divers were metabolizing it.

This is a really interesting point. How big would a cave need to be in order to support the oxygen requirements of a single human? I assume surface area of the water is the important factor?

Re: Two days in an underwater cave running out of oxygen

#234

Post by [deleted] »

gameshot911 wrote: post #215
A_Person wrote: post #208

I'd like to address the false assumption in this thread that cave diving is more dangerous than driving a car! I cave dive on a regular basis with two other guys. We've dived together as a team for nearly 10 years. I'm late 60s and single, the second guy is 50s and has a partner but no children, and the third is early 40s with a six-year-old, who he has every intention of seeing grow-up into adulthood. We often dive…

Can you share the most dangerous moment you've ever been in, despite all precautions?

[deleted]

Re: Two days in an underwater cave running out of oxygen

#235

Post by Leslie54 »

laumars wrote: post #172
pragone wrote: post #166

Earlier quoted context omitted.

> Given the choice of having a father at home or have one dead in cave but famous for exploring cool places I don't think it's hard to guess what most children would pick. In all seriousness, I do have a hard time guessing which one most children would pick. I can see reasonable arguments made on either side. Personally, I think it would be far more inspiring to have a father who died pursuing his passion, then one w…

Depends on the kid, their age and their relationship with their father. I don't think there is any right generalized answer. With my kids I know they would rather have me around, but they are young so I'm already "superman" to them. Who knows how our relationship will change as they grow older.

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Re: Two days in an underwater cave running out of oxygen

#236

Post by A_Person »

gameshot911 wrote: post #215
A_Person wrote: post #208

I'd like to address the false assumption in this thread that cave diving is more dangerous than driving a car! I cave dive on a regular basis with two other guys. We've dived together as a team for nearly 10 years. I'm late 60s and single, the second guy is 50s and has a partner but no children, and the third is early 40s with a six-year-old, who he has every intention of seeing grow-up into adulthood. We often dive…

Can you share the most dangerous moment you've ever been in, despite all precautions?

Sure :-)

Objectively speaking, the most dangerous moment I've ever had scuba diving was in a straight-sided sinkhole, with no overhead environment at all, doing a refresher course, for the first (most basic) level of cave diving, after a few years off! Some unexpected things went wrong, and I suddenly realized that I was seperated from the group, 40 meters deep, silted out, tangled up, and the scary part: hyperventilating like crazy, and absolutely about to panic. It took every ounce of 35 years of diving experience to keep it together, which I only just managed to do. It was amazing how quickly it went from totally cool, to totally about to panic - it felt like only seconds. It taught me that I'd got MUCH TOO COMPLACENT, and needed to refocus things. This was quite a few years ago, and I felt the effects for several years afterwards.

A later expeience was when I went through a small restriction that I and my buddy had been through several times before. For some reason, my buddy couldn't get through this time, so I turned back - and couldn't get out! Try as I would, it just wasn't happening. I'd go in, get stuck, back out, check my gas, close my eyes, wait for my heartrate to go back down, then try again. After maybe 10 minutes trying, I eventually managed to wiggle out. Now I wear my tanks "side mounted", so I can unclip one or both of them to reduce my profile.

A few months ago, a buddy and I were diving with another pair. We were in front, they were behind. Then they disappeared, so after waiting a while, we turned back to see what had happened. I then found that the tunnel we were going back through, was completely silted out (perhaps 6 inches visibility), and the fixed line seemed to disappear under a rock, into the ground! I couldn't find where it came back out. In our part of the world, you're hung drawn and quartered if you touch the cave - anywhere - at all; but stuff that, I heaved that big sucker off the line, which happily sprang back into place, so we continued into the murk!

The last two examples might seem a bit scary, but those kinds of situations are just part of the learning process in cave diving - every competent cave diver is equipped and trained to handle such things. The first example, mundane as it may sound, was the one that really scared me.

Shall I book you a place on the next course? :-)

[edit: spelling]

Re: Two days in an underwater cave running out of oxygen

#237

Post by harperlee »

aesh2Xa1 wrote: post #160
andrewfong wrote: post #134

Earlier quoted context omitted.

> Given the choice of having a father at home or have one dead in cave but famous for exploring cool places I don't think it's hard to guess what most children would pick. Not that it necessarily changes the argument, but the "choice" is probabilistic. That is, it isn't father at home vs. dead, but "probably boring dad but most likely alive" vs. "maybe famous dad but some chance of death".

That doesn't sound right. How many cave-going dads are there that you could make the claim? And do a majority of kids believe their fathers are boring? I just don't buy it. And is taking a risk like this the best way to be "not boring?" Definitely don't buy it. You can have fun and be adventurous without taking heavy risks. It's fair to say that someone who continues to put himself at harm is foolish in one capacity…

I think the grandfather post is mainly saying that not thinking this through a lense of risk and reward, that can end up giving kids some good outcome is an error (and for sure having a happy father IS better than a depressive one, so if the cave diving risk is sufficiently low, then it makes sense to do it). This line of thought is also probably similar to what that guy thought (to think it is worth the risk to live like that). In that case, you have a slope of risk that starts reasonably and ends up unacceptable, but where you can't easily pinpoint where to draw the line.

Whether you "buy" the simple causal graph that he used as an example is a minor point.

Re: Two days in an underwater cave running out of oxygen

#238

Post by ajross »

mulmen wrote: post #233
ajross wrote: post #5

Earlier quoted context omitted.

The air in the cave will come to equilibrium with the partial pressures of gasses in the water, which itself is in equilibrium with the atmosphere. It's not as closed as system as you think, even though it probably wouldn't outgas oxygen as fast as the divers were metabolizing it.

This is a really interesting point. How big would a cave need to be in order to support the oxygen requirements of a single human? I assume surface area of the water is the important factor?

Also the level of circulation of the water connecting it to the ocean/aquifer. Diffusion is a ton slower than convection.

Re: Two days in an underwater cave running out of oxygen

#239

Post by jonahx »

chii wrote: post #222
jonahx wrote: post #214

Earlier quoted context omitted.

If you just asked them, in all their ignorance, you're undoubtedly right. If you asked the children who chose the adventurous dad after he had died pursuing his passion, nearly 100% would trade the world to reverse that choice.

That's an inherently biased question, because they've already suffered the loss, and so would've chosen not to suffer it given the chance. The same thing (but reverse) with asking children whose fathers didn't go on an adventure and see if they would've preferred a more adventurous father!

I'm sorry, but this is a kind of clever sophistry that is absurd in the face of lived experience...

> The same thing (but reverse) with asking children whose fathers didn't go on an adventure and see if they would've preferred a more adventurous father!

Yes, each child only knows one half of the story, as it were. But the knowledge imbalance is not symmetrical. The child whose father has died understands boredom and dissatisfaction in other ways... perhaps his mother is boring, or sometimes nags him, and even his adventurous (now dead) father surely disappointed him sometimes, and so on.

The child who has not experienced death really has no idea what that suffering is like. It's just utterly callow to think his opinion has equal weight.

Re: Two days in an underwater cave running out of oxygen

#240

Post by stingraycharles »

titanomachy wrote: post #31
biggc wrote: post #19

> He realised the water at the surface of the lake was drinkable Can someone explain this phenomena? How can the water in a sea-cave become potable?

I'm not familiar with Mallorca's hydrogeology, but I've done some cenote (cavern) diving in Mexico's Yucatan peninsula. The caves are inland, but sea water infiltrates through the porous and channel-filled rock. The water nearer the surface is rainwater. The narrow region where freshwater and seawater intermingle is called the halocline, it creates a cool optical distortion which reminds me of the "oil paint" filter…

This probably is a stupid question, but wouldn't the salty seawater be lighter than the rain water, and thus be at the surface ?
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