Why does a block of plastic released underwater come to the surface?

We know that when a body is fully or partially immersed in a liquid, a buoyant force will act on it in the upward direction. When this buoyant force is greater than the force of gravity acting on the body, the body will rise to the surface of the water. The buoyant force is greater than the force of gravity for materials with a density smaller than water. Since the density of plastic is typically less than the density of water, the buoyant force acting on the plastic block is greater than its weight, causing it to rise to the surface of the water.