If I understand it correctly, liquids such as water, in general have a natural state of distributing itself evenly over the largest possible surface area. While certain effects such as hydrogen bonding make "clumps" or pools of water, it is understood when you poor water out of a cup, it distributes straight down to the floor and not up to the ceiling. The rate, the force, the impact, are all depending on the acceleration of gravity. In the glass container each of these molecules are often macroscopically treated as a single body as true liquid dynamics aren't necessary to derive the pressure. Again pressure simply being the Force over an Area. In this case, Force is dependent on some molecular forces, but generally its just the Force of Gravity necessary to take into account.
Gas on the other hand has a different natural state to occupy as much space as possible in all directions. And when you observe Gas in a container, Pressure, which is still Force / Area, has a lot of different variables working on it, and that pressure is now omni-directional. Gravity is still there, but Temperature, Volume, number of Moles etc., change the state of the Gas. So basically pressure for a Gas would stipulate that you are observing an average of pressure on all the walls of the container, taking into the account of Atomic / Molecular Collision, Gravity, Avg. Kinetic Energy etc etc.
One more thing is that most liquids do not compress, there is displacement. There are a finite number of molecules at every layer in each of these ponds. No more, no less. They are not pushing on each other, they simply fill the gaps. The water you occupy in your 3 meter depth, is diverted upward at the surface since it can't compress downwards or sideways. You sit in the bathtub and water rises. What this correlates to, there is no more pressure replacing that water with your body. However, having 3 meters of x kg water on top of you, will weigh down on you. You also have y kg water below you countering that weight. At the very bottom of the pond you have all of x + y kg of water applying a downward force on top of you. As you can see it isn't pressure via compression on you, but the weight of the water creating pressure. Which relates back to just the Force of Gravity on you. Now most of these basic problems never force you to calculate the area of water or the weight of the water, they simply give you usually an initial Pressure, P0, and then the density of water, gravity, and height, and then you have to determine the new pressure.
P = P0 + Rho * g * h
I find that starting off with the equation above is a little bit silly as it takes work on the user to understand the formula / units. Where as if you explain things first by a simple concept as mass or weight, on top of something else, its much easier to relate to. The equation above skips find Mass, Force, and then area, it just goes straight to Pressure, which is Force over an Area. I guess its just a different approach in teaching the subject matter.
