Responses (2)
All the fluid (air or water) above a point weighs down on that point and what's under that point pushes up with an equal force. If not so, the body would move in the direction of the greater force. If the body displaces fluid, then the force is changed by the weight of the fluid displaced. If the displaced fluid weighs less than the body then the body sinks. If not then the body floats.
The upward force is called the buoyant force.