the centre of pressure on an immersed plane surface is always below the centre of gravity of the surface because the pressure increases (linearly) with depth below the water surface; if pressure was constant with depth, the centre of gravity and centre of pressure would coincide.

the hydrostatic force acting on a vertical wall depends on the depth of the water being impounded but not on the lateral extent (away from the wall) of the water being held back 

in an inclined tube filled with fluid, the pressure difference between the top and bottom of the tube depends only on the vertical elevation difference between the two ends.

In the formula for the hydrostatic force acting on a plane surface, F=γ A h_cthe following definitions apply: h_c = depth to the centroid of the pressure diagram acting on the plane surface, A= immersed area of the plane surface, (gamma) γ = ρ.g and (rho) ρ = density of the fluid.