The stranding of a dozen kids in a cave filled with water is a good opportunity for inventing rescue innovations. Unless the cave is too tight there should be some sort of thin capsule with an oxygen supply to stick a kid in and let the Thai Seals push/pull it out, one kid at a time. How much pressure could there be in that 2.5 mile long cavern? Would it be practical to make a capsule that can articulate to flex to get through tight spots?
Maybe the capsule should have some video game to distract the user so they relax the six hours during transit out of the cave. With a world of spectators one would think there should be some bright-ling able to open the door.
pea pod image credit;By Rasbak – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=194762