Why fish appear at less depth than actual position in water?

This is due to a phenomenon called refraction, which is the bending of light as it passes from one medium to another. Here's how it works:

* Light travels at different speeds in different mediums. In air, light travels faster than in water.

* When light travels from water to air, it bends away from the normal. The normal is an imaginary line perpendicular to the surface of the water.

* This bending of light makes the fish appear higher than its actual position.

Here's a simple analogy: imagine you're looking at a straw in a glass of water. The straw appears to be bent at the point where it enters the water. This is because the light from the straw is bending as it travels from the water to your eyes.

The same principle applies to fish. The light from the fish bends as it travels from the water to your eyes, making the fish appear higher than it actually is.

Here's a more detailed explanation:

1. When light from a fish travels upwards towards the surface of the water, it encounters a change in medium (from water to air).

2. Since light travels slower in water, it bends away from the normal (the imaginary line perpendicular to the surface of the water).

3. This bending causes the light rays to reach your eye at a different angle than they would if they had traveled in a straight line.

4. Your brain interprets these angled light rays as coming from a higher position than the fish's actual location, resulting in the fish appearing shallower.

This effect is more pronounced at steeper angles of observation (when you're looking at the fish from a more oblique angle).