10-20m What color is the fill light for deep-water photography?

The color of the fill light is blue-cyan.

Water absorbs red and orange light most seriously, followed by yellow, purple and green light, while blue and cyan light is the weakest. The colors of light seen underwater are usually blue and cyan. Therefore, the photos and TV images taken by underwater color photography tend to be Lan Qing or blue-green.

During the propagation of light in water, the intensity will gradually weaken due to the absorption of water, and this absorption of light by water is related to the wavelength of each monochromatic light, so the blue-cyan fill light is used in the deep water of 10-20 meters.