No one seems to mention this for whatever reason, but the diagrams of the cave show three or four dry areas out of the water. Presumably they would be used as brief rest areas.
On a twitter site with a diagram they said 3 hours of underwater swimming! And it looked like three major flooded areas to go through. I’m guessing at least one of those would require changing a tank out - underwater??!!
I’m not trained, but went scuba diving once. It was fine - due to my ignorance no doubt! Plus - if I got into trouble all I had to do was swim up 20 feet or whatever to all the air in the world. I can’t imagine doing it for the first time in the dark, not being a swimmer, and then having to change tanks.
Dear God - give those kid’s the courage and will and calmness that they will need.