Refraction of light
As light travels from air to water, it bends, or refracts. This bending of light causes objects in the water to appear closer to the surface than they actually are. The amount of refraction depends on the angle at which the light strikes the water and the difference in the refractive indices of air and water.
Absorption of light
As light travels through water, it is absorbed by the water molecules. The amount of light that is absorbed depends on the wavelength of the light and the clarity of the water. Shorter wavelengths of light, such as blue light, are absorbed more quickly than longer wavelengths of light, such as red light. This is why the water in a pond appears blue or green.
Scattering of light
As light travels through water, it is scattered by particles suspended in the water. These particles can include sediment, algae, and plankton. The scattering of light causes the water to appear cloudy or murky.
The combined effects of refraction, absorption, and scattering of light make the water in a pond appear shallower than it actually is. This phenomenon can be a safety hazard, as it can lead people to underestimate the depth of the water and potentially drown.