Comment by dm319 | Hacker News Reader

Comment by dm319 | Hacker News Reader

This is great news, but sadly their lives are still very much at risk. They are too deep to drill down to, there is a lot of rain to pump out (and the rain can continue), and they can't swim (even if they could, this is a hard dive for those that can).

Found this from a Bill Whitehouse:

Bill Whitehouse, vice-chair of the British Cave Rescue Council which is helping the rescue efforts, played down speculation the boys could be taught to dive.

Speaking to BBC Radio 4’s Today programme he suggested they could be guided through the water in “packages”.

Asked how feasible it would be to teach the children to dive, he said: “It is certainly not easy. The other alternative is that you literally bring them out in packages. In other words you fit them with diving equipment: a full face mask, instead of having a gag in your mouth like a lot of divers use; package them up; put the correct weights on them so that they are neutrally bouyant and are not going to get stuck again. It has been done before.”

He also explained how the British divers reached the trapped group.

    They were diving upstream in the system so they were having to swim against the current,
    or pull themselves along the walls. Some of the cave is fairly constricted and other points
    aren’t. I gather the actual diving section was about 1.5km, about half of which was
    completely flooded and about half of which was open.

    They estimated that a round trip to where the party was and back again is probably about three hours.

Whitehouse was sceptical about the prospects of pumping enough water out of the cave to allow the boys to walk to safety. He said: “They are trying to do that with pumping, but pumping a monsoon away is not that easy.”

As an experienced cave diver, I agree with Mr Whitehouse that bringing them out as "packages" should be considered an option. It would be easier than allowing them to swim by themselves in murky waters with no vision. The diving training spoken of might be getting the boys to be used to being towed under water while being packaged up, rather than about teaching them about buoyancy control like adult divers.

You can't be serious. Taking 13 people, with an absolute maximum of Open Water level training (if that), back out through hundreds (or thousands?) of meters of low or zero visibility diving, including (apparently) tight restrictions, without risking the lives of all concerned? Aint gonna happen - unless the water level drops to the point where they can just float back out.

What I don't understand is that surely there must be a wide enough passage for them to have got in in the first place. It may be flooded but if one can walk into them vertically, surely they should be fairly accessible to a diver horizontally. Can't they just follow / be attached to a string or something like that?

Current and silt, I imagine

Think about thin vertical passages. You can talk trough them easily but diving would be very difficult.

I know nothing about that cave, but passages between caves can be connected by tight restrictions. They might have crawled they way up. And now that restriction is flooded.

Add a bunch of regulator hoses, fins, air supply etc to someone not used to having them attached and the gap needs to be huge to not snare a hose and rip a full face mask off.

Even a semi experienced diver is far less aware of all their apparatus than a human who has been crawling around things since birth

It's not logically following to me that just because it's easy to walk through a place it must necessarily be easy to dive through it. Diving is always significantly harder (you're wearing bulkier equipment for starters). It costs more energy to swim through water than it does to walk through air, the water has currents which you have to fight against, and the waters are murky so you have to go slow and can easily get disoriented.

You have those small engines/jets/scooters for divers, so exhaustion from swimming should not be a problem, right? They also can place long glowing ropes in murky water; it's been done all the time in caves (or bind them to scuba divers, one in front, one in the back of a group). Once those boys get proper proteins/water and wait for a day or two to recover, they should be able to work it out, unless rain picks up - they are old enough to be considered adults in some Asian cultures, perfect age for an adventure of lifetime. But then even their current position is under danger as it could be flooded further or if a large flash flood occurs, then all bets are off.

I'm no expert but I don't believe those diving jets are going to help in such an environment because A) takes up space of which they most likely don't have and B) it kicks up a lot of silt and dirt, making visibility conditions terrible. This can make or break such a rescue attempt and be really dangerous even for a seasoned cave diver.

This doesn't seem so bulky: http://www.businessinsider.com/handheld-jet-thruster-propels...

And DIY versions abound: https://hackaday.com/2017/07/02/the-almost-working-diy-under...

Note that the article states:

> Narongsak explained that the divers had fixed rope lines along the passageway and distributed oxygen tanks along their route, allowing them to advance through the exceptionally narrow passageway unencumbered by bulky equipment.

The (extremely skilled) divers aren't wearing tanks due to how narrow some parts of the passage are. Using a thruster in a cramped environment is not a silver bullet.

Could it be that the route divers explored != the route the group has taken? So they might have descended using much more difficult route than the one the group took?

Unlikely. I am a Thai so I have been reading a lot of info since the beginning, and most people initially suggest that they shouldn't be in too deep since that Monk junction section is very narrow, steep, and hard to pass, even on foot.

It comes out later that the group frequent this cave many time before.

It's a 2.5 km (a bit less than 2 miles) underwater swim. Right now they've been without food for 10 days and are barely able to stand. At the moment they wouldn't be able to walk the distance, much less spend many hours (it was about four hours for the experienced divers, so more for the boys) swimming underwater in unpredictable currents with no visibility due to silt, so if they get confused and let go of the string for a moment in those hours then they die.

As one of the rescuers said, "When it starts raining the flow is so hard you can barely swim against it." - and that's a pro diver, imagine how would it be for a boy who didn't even know how to swim and thus doesn't have the relevant muscles trained. It's also narrow enough so that only one person can fit through, so you can't have the divers guide them by hand, only accompany them behind them.

”only accompany them behind them”

I think they would have them tied to a rope between divers, so that one of them can pull (gently, in narrow areas) and the other can guide the package to prevent it from scratching the rocks.

Fortunately the current is in the direction that they need to go to get out.

Not really - from the plan (https://www.theguardian.com/world/ng-interactive/2018/jul/03...) it seems that it's about 50/50; first they need to go ~700m against the current and only then ~800m with the current.

Why hasn't food been delivered?

The food has been delivered after they found the group.

My wife and I were doing a dive under very controlled circumstances. My wife tried to swim through a circular opening wider than your outspread arms. She couldn't. Fighting panic (rule 2: dont panic!) She kept trying, growing ever more aware of being both underwater and underground.

Then our dive master reached out and pushed her down a foot, and suddenly her tank could clear the top. From her perspective she kept swimming lower, but that was counteracted by buoyancy and she couldn't tell, with every failed attempt reducing her mental capacity to figure it out.

Fight or flight is not the reflex we need in diving, but it is the reflex we have.

I don't know that cave at all, but from various descriptions, it sounds like they may have had to crawl through several restrictions to get where they are. So it's not a matter of walking through vertically to get in, then just being gently pulled back out the same way It's a matter of squeezing through on your belly to get in - then to get out, reversing that, in unfamiliar bulky diving gear, completely underwater (literally no air anywhere), in pitch blackness, and zero visibility (as in, you'd not see an inch beyond your mask, even with a powerful torch). It's not easy even for experienced cave divers. I once went through a hole, then couldn't get back out! I tried for 10 minutes. At one point I even considered removing my tanks and pushing them out first. It eventually happened, but it gave me a scare - and that was in crystal clear water, in a site I'd dived before! Its just not as simple as people seem to assume. But again, I don't know the cave in question, I'm just going from what I've read.

Can't they run an oxygen hose to the place? Or perhaps bring a bunch of oxygen tanks, which could be used until they figure it out?

They are (or were) planning for the possibility of the group having to stay down there for months to allow the rainy season to pass, while being re-supplied by divers.

Use indentation only for code, not blockquote

> They were diving upstream in the system so they were having to swim against the current, or pull themselves along the walls. Some of the cave is fairly constricted and other points aren’t. I gather the actual diving section was about 1.5km, about half of which was completely flooded and about half of which was open. They estimated that a round trip is 3 hours.

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