When you sit in the dark, even a small drip of water into a pool can make noises that can mimic almost any sound you can imagine… they sat like that for 9 days… I can imagine that they had no difficulty dreaming up all sorts of things… still I can think of places where odd things have helped find an easy if dangerous way out of a cave system… the oddest was a sudden strong odour of gasoline… people went looking to see where it was coming from… it was unmistakeable… they soon saw light and crawled out. that is the rescuers… and found that they had passed under a farm yard and the owner had spilled some while fueling his truck… and since at that point the cave was only a few dozen feet lower… it went straight into it…
Needless everybody wanted out ASAP… It was after finding the way out that it they learned it had only been a few drops that got away… thankfully… I wasn’t there and most people inside were able to switch to electric lamps… they had been using carbide… duh. The landowner knew of the cave, but never associated it with being connected to the search site… forget where it was… somewhere in the southeast… TAG country I think… TN AL GA… that is.
As for the Elon Musk thing… not really a sub in the usual sense I think… more like a water tight box with an air supply… probably aimed at the younger ones… but I don’t have any information on the size… but it is probably there on SpaceX site.
I think it is good idea but as you said they have a good idea of Width and Depth dimensions, but if you have ever moved a couch, length can be limiting… one could send a test object ballasted and adjustable to test the limits… I think the older boys could handle the diving thing without it… but all kids can surprise you… and adults.
I remember way back they had a stretcher (Neill-Robertson) that was originally designed for the Navy… and intended to be used taking subjects through portholes of a certain size… was also good for hatches etc. They were using them in England for sump rescue… tank between the legs and a face mask… but not on this scale.
I did notice that they were excavating some of the passage walls…a bit but today it said that they were enlarging a drain tunnel experimentally to increase flow. Wondering if they tried smoothing out that tight section… but they might have accidentally blocked it… given Mr. Murphy… and didn’t risk to much… Time will tell, i was just watching an Eastern tv news from Ontario… seems they are underway now! but I haven’t confirmed that report or when it was broadcast… but it was only the CTV continuous news service… got to run.
Edit: just saw a full report of the same thing… the other one was a popup… this was a story… says a mix of civilian cave rescue divers and military have been heading into the cave… because… they have the lowest water levels in weeks and there is heavy rain nearby… no time for subs or drilling holes. @TerriB I did see that they have been using an underground radio to fix a position for such a project… I suspected they would get one in… my generation ones were massive in size, hopefully 30 plus years has allowed improvement… they work like avalanche beacons… when you get the antennas aligned to max signal, they are in line and one is directly over the other… or supposed to be… lots of room to miss in the old days… Night folks