Why apparent depth is less than real depth?

Apparent depth is less than real depth due to the refraction of light as it passes from water to air. When light rays travel from a denser medium (like water) to a less dense medium (like air), they bend away from the normal, making objects submerged in water appear closer to the surface than they actually are. This bending of light causes our perception of depth to be distorted, leading to the phenomenon where objects look shallower than they truly are.