I put a weighted hose pipe into the flooded pipe, duct taped my little Miele vacuum cleaner to it, remembering to take out the bag of course. Do t want a soggy bag.
then switched on the vacuum cleaner to blow on low pressure to get the back flow working. Obviously nice clean air going down the airline for the boys will help.
The clean air should bubble up into the cave. The backdraught should suck out some water.
Couple a com line and a feeding tube to the air line. And take them some IPads and games to play. They can learn all about scuba diving off YouTube. These boys seem very resourceful.
Hope this works on the scaled up version. Obviously with the com line in you need some monitoring equipment for the air pressure and risk analysis.
Yup, it’s Fluidics! My Dad taught me a lot of things.
If you do use a vacuum cleaner to blow air down the pipe, remember to find some way to evacuate the chamber as well. You might need to actually suck air pressure out of the big chamber. Well it would work better if you did I suppose.
My Dad was a Genius. Artistic, and totally brilliant. He was a very brave and honourable Man.