This thread on diving Bushman’s Hole (fascinating and tragic story) got me wondering, does the geometry of the cave affect the water pressure? There is a narrow chimney that opens into a large chamber below 150 feet. Is the water pressure at, say, 160 feet in the chamber the same as it would be if the cave were a uniform diameter all the way up?
My first way of thinking about it is, at 140 feet in the chimney, it feels like 140 feet of water above me. I wouldn’t think the pressure would decrease when I go down into the chamber, so the pressure should be independent of the shape.
But then I think, what if the chimney were very narrow, like 1 inch in diameter? I could fill the entire 150 feet with just over 6 gallons of water. It doesn’t make sense that the pressure in the chamber could change by ~4.5 atmospheres by adding that amount of water to the chimney.
I’m obviously wrong somewhere. Where is the flaw?