# Does the pressure increase under an upturned glass?

During my children's bath time we were playing with an upturned plastic jug filled with water and making some plastic divers float up inside the jug - see image.

If one of the divers swam from A to B to C, would the water pressure on them remain constant? Or would it increase at B because of the higher column of water above?

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As an extreme example, if the surfaces at A and C are at pressure $P$ and the height of B is more than $h=P/\rho g$ (about ten meters for water at one atmosphere) you'd pull a vacuum at the top surface of B. –  rob Jun 9 '14 at 12:31
Another thing: the water level at A and C is slightly lower than it would be if you dumped the jug. This means the air pressure is slightly ( $\epsilon$ :-) ) greater now than it will be when the jug is dumped. The mean pressure over the entire bathtub-jug top surface will remain the same, I believe. –  Carl Witthoft Jun 9 '14 at 13:34