The soccer kids reported hearing sounds from outside as soon as the divers found them. Rescuers should really try to find out if there is a back passage somewhere. They could just form a massive grid pattern about where they think the kids are but above ground, and shoot a gun as they walk the grid. If anybody in the cave hears them, they stop walking. Then each member of the search party shoots in turn. If there is a hole, they could locate it very quickly.

This has the great advantage of letting hundreds of people help in the rescue, not just a few advanced scuba divers.

Another thing they could try is to release some distinctive odor inside the cave. Then let dog teams go over the outside to locate the scent. I would suggest drug-sniffing dogs since so many of them are already trained to locate those specific scents. Also they are so sensitive, you wouldn't have to drug everybody in the cave. Just use a little bit of cannabis or opium.