Have you ever noticed how the water in the bath rises when you get in? This happens because your body weight pushes the water aside, or displaces it.
What happens when you get into a larger body of water like a swimming pool? You’ll float! Your body pushes aside enough water to equal your weight. But the water also pushes back against your body, so you float! This is called buoyancy. Buoyancy is the upward push of displaced water.
If you could weigh the water your body displaced, it would be equal to the pressure of the water pushing up on your body. The pressure pushing up cancels out your weight pushing down.
So why do some objects sink? Objects that are heavier than the same amount of water sink in water. When you throw a rock into the water, it weighs more than the amount of water it displaces, so it sinks.
Picture Credit : Google