Why does water makes things look closer?

Consider a 12 inch ruler held vertically, positioned 6 inches from your eye. Now imagine two beams of light coming from the top and the bottom of the ruler, converging at your eye at an angle of 90 degrees. Your perception of the size of the ruler is determined by the angle between these two beams of light. Now image the ruler is moved back so it is 1 foot (twice as far) from your eye. The two beams of light from the top and bottom of the ruler now converge at an angle that is twice as small, 45 degrees. Therefore, the apparent size of an object is indirectly proportionate to the distance from the observer.