Eli5 : if pressure is due to the size of the column of fluid above, why is it not lighter inside ?

Question

I know that if you are inside of a hermetic room, the pressure is the same. But I can’t understand *why*. For example, if you enclose water from the bottom of the ocean in a box, shouldn’t it be suddenly at the same pressure than outside, due to the fact there is not the weight of the water column above ?

Thanks!

In: 2

Answer 1

If you enclose water at the bottom of the ocean in a box, then the column of fluid above it is applying pressure to the box, which applies pressure to the water within in.