Hydrostatic Pressure

If you've ever gotten an earache when at the bottom of the pool, then you've experience fluid depth pressure. Plugged ears can also be attributed to this phenomenon(remember, gases are also considered fluids). This phenomenon is due to the fact that you're experiencing the pressure caused by the weight of everything above you. The reason you don't feel it when you're on the ground is that the pressure above you is atmospheric pressure, which is caused by air that isn't very dense.

This expression is the pure expression for the pressure of a fluid at depth h. This is important because many might confuse themselves and claim the fluid pressure on an object is greater or lesser due to differences in cross-sectional area or volume.

However, as proven by the equation above, it really is only dependent on height, assuming the object's height above the Earth's center of mass doesn't change drastically to the point where g changes. However, if you discuss deep-sea submarines going many miles deep into the ocean, then you may have to account for differences in g. This makes since because gravitational acceleration isn't surface levels any more and can be significantly different.

Note that the depth h is the depth the object is submerged into the fluid. ⍴ is the density of the fluid the object is submerged in. This is not the density of the object in the fluid. If you need the average pressure, you use P = ⍴gh, except you use the average height instead to be accurate.