So say I had a glass of water on a table ,with the glass filled to the top. The bottom of the glass, the water would have a higher pressure than the top of the glass. This is the concept of hydrostatic pressure etc. But how does GPE fit into all of this? Does the water at the top of the glass contain more GPE than the water at the bottom? If that is the case, how can there be equilibrium (assume there is no net movement of water) in the glass of water when the derivation of the hydrostatic pressure only takes into account the pressure of the water and its weight above a certain fixed point?