Good illustration!
I think the key to understanding the danger is to see the first (or last, in their case) restriction where it says “Passage is too narrow for diver to wear oxygen tank”.
Depending on how narrow and how long this passage is, is it possible to widen, or do they just need to bring them here, and figure out the quickest way to get them through?
How the heck did they wind up way back there?
Why did they keep walking into that cave for 2 miles?
Rock is rock.