The Archimedes' principle was named after Greek philosopher Archimedes. The principle is closely related to buoyancy as you can see in the statement below.
Here is what Archimedes states:
Whether the object is partially submerged or not, the principle is still true.
For example, suppose you submerge a rock in water whose weight is 10 pounds and the water that is displaced has a weight of 4 pounds, what is the buoyant force?
Since the rock displaced 4 pounds of water and the buoyant force is equal to the weight of the liquid that the object displaces, the buoyant force is 4 pounds.
Notice that it is not the weight of the object that determine the buoyant force, but the weight of the displaced water. This situation is illustrated below:
The strength of the force beneath the rock that pushes the rock up is equal to 4 pounds.