Camouflage is a creature making a good match with its surroundings. This serves to conceal it from both predators and prey. In the water, there are many exponents of this approach, from octopuses to scorpionfish.
Flatfish are masters of camouflage. It’s a fluke to see a stationary flatfish. It’s almost always necessary to see one on the move and to track it to where it settles down. Once it’s set though, it will usually stay put, making it one of the easier fish to observe and photograph.
I saw this flowery flounder on the move but once it plopped onto a rock (above) I would never have noticed it had I not known it was there.