Archimedes Principle states that when a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.
We can observe it by the following activity:

● Tie a stone at the end of a spring balance.

● Suspend the stone in air by holding the spring balance and observe the reading of the spring balance due to the weight of stone.

● Now, slowly immerse the stone in water in a container.

● As the stone is lowered in the water, the reading of spring balance decreases.
As we know that the reading of spring balance is due to the weight of the stone. The decrease in reading of the spring balance shows the loss in weight of stone due to some force acting on the stone in upward direction. This upward force exerted by the water is equal to the weight of water displaced by the stone. This approves the Archimedes principle.