Why does the transition of light waves from water to air make it seem as if fish and other things in a pond are shallower then they actually are?

An object seen in the water will usually appear to be at a different depth than it actually is, due to the refraction of light rays as they travel from the water into the air. This tutorial explores how fish, observed from the bank of a pond or lake, appear to be closer to the surface than they really are.