Underwater camouflage

Underwater camouflage is the set of methods of achieving crypsis—avoidance of observation—that allows otherwise visible aquatic organisms to remain unnoticed by other organisms such as predators or prey.

Camouflage in large bodies of water differs markedly from camouflage on land. The environment is essentially the same on all sides. Light always falls from above, and there is generally no variable background^[a] to compare with trees and bushes. Near to the sea surface reflectivity and blue coloration are the most common form of camouflage. Below, countershading is more common, with blue coloration on the dorsal side and white on the ventral side. Below the epipelagic zone transparency is more frequent. In the aphotic zone red and black coloration are common, often in combination with bioluminescence. At the very deepest areas such as the benthic regions of the hadal zone, most animals use pale red and cream colors.^[2]

Camouflage in relatively shallow waters is more like terrestrial camouflage, where additional methods are used by many animals. For example, self-decoration is employed by decorator crabs; mimicry by animals such as the leafy sea dragon; countershading by many fish including sharks; distraction with eyespots by many fish; active camouflage through ability to change colour rapidly in fish such as the flounder, and cephalopods including octopus, cuttlefish, and squid.

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