When a wooden cork is pushed below the water's surface, it displaces a volume of water equal to its own volume, creating an upward buoyant force. While the finger applies downward force, the cork remains submerged. 

Once the finger is removed, the buoyant force exceeds the weight of the cork, causing it to rise to the surface.

 This phenomenon illustrates Archimedes' Principle, where the buoyant force acts on objects submerged in fluid.