Color becomes visible when certain wavelengths of light reflect off an object. Colors change quite dramatically underwater. The wavelengths of light bend or are filtered out. Long wavelengths, such as red and orange, are absorbed by water. Short wavelengths, such as blue, are scattered. This gives clear water its blue appearance.
In murky water, there is less light penetration. Things have a greenish-yellow appearance. If you were to cut yourself, the blood will look green or brown. Even under the best conditions, colors will fade the deeper you dive. The way colors are absorbed impacts underwater photography. A good light source is needed for vibrant images. Photographers often use a red filter to get images with deep natural light. The filter helps remove some of the blue color.
The sun’s angle also has a direct effect on visibility. The water surface can behave like a mirror. When the sun is directly overhead, most of the light will enter the water. But at dawn and dusk, the light may reflect off the surface. It may also not penetrate the water.