Countershading

Counter- shading, also called Countershading, is a special form of camouflage (biology), which reduces the predation risk. It is to be found especially among residents of three-dimensional habitats. For example, floating in the sea penguins difficult to see from above, because their darker back visually merges with the dark water. Viewed from below, they are not clearly visible to predators with their bright belly against the bright sky.

Counter- shading is to be found in many fish species. Also some Artiodactyla have skins with counter shading.