The Nature of Fluid Pressure
Particles of a fluid exert pressure upon each other and upon objects immersed within or floating upon the fluid. The pressure at any given location within the fluid is dependent upon the density of the fluid and the height of that location below the surface of the fluid. Pressure is greater at deeper locations and greater for more dense fluids. The depth is measured vertically downward from the surface.
Fluids press upon each other. Fluids press upon immersed and floating objects. Fluids press upon the walls and the bottom of the container. At any given location, a fluid presses in all locations, causing a force that is equal in each direction. At the walls and at the bottom of the container, the direction of the resultant force is perpendicular to the container's surface.
Because pressure varies with depth, objects immersed in a fluid will experience a different force on its bottom surface than on its upper surface. This difference in force results in a so-called buoyant force on the object that buoys the object in the upward direction.