Pencil in glass of water
Reds are the first colors to be absorbed.
Refraction is a property of light that refers to the change in the speed of light due to change of density in a new medium. This causes a change in the light's path. An example of this is given by looking at a pencil partially submerged in a clear glass of water. The pencil appears as if it is bent. This is because the path of the light you are seeing changes when the light passes through the water. While underwater, this property can make things appear closer to you than they actually are.
While refraction can make things appear closer to you than they actually are, turbidity, or the concentration of suspended particles in the water, can make objects appear further away than they actually are. This is referred to as visual reversal.
When light strikes something, it may be reflected or absorbed. The amount of light reflected or absorbed can depend upon the substance that the light is striking. For some substances such as water, the amount of light reflected is related to the angle at which the light hits the surface of the water. When the angle between the light source, in this case the sun, and the plane of the surface of the water is 90 degrees, almost no light is reflected. As this angle decreases, a greater amount of light is reflected. This is why a diver in relatively clear water will experience brighter dive conditions at noon than at twilight.
The colors that we see all have different wavelengths. These wavelengths relate to the amount of energy in the light. As light passes through water, wavelengths with less energy are more easily absorbed. Because of this, the deeper a diver descends, the less colors that he or she can see. When underwater photographers take photos, they use powerful lights to illuminate their subject. This introduces a new, closer light source thereby 'reintroducing' color.
The speed of a sound wave depends upon the medium that the wave is traveling through. Sound travels more efficiently as the elasticity of the medium through which it is traveling increases. In nature we find that dense materials tend to be very elastic. Therefore, since water is more dense (and more elastic) than air, sound travels faster in water. The speed of sound in water is about four times as fast as its speed in air. This makes it difficult to determine where a sound is coming from when you are diving. This is because your brain bases sound direction on intensity with which you hear the noise and the time it takes to reach one ear and then the other. It can become confused when sound is traveling faster than normal.
Rendering of sound waves