Why many deep sea creatures are red?

Color depends on the light that reaches an object

An object looks red near the surface because red wavelengths strike it and are reflected to an observer. Deeper down, those wavelengths have already been absorbed by the water.

Without red illumination, red tissue returns almost no visible red light and looks dark gray or black.

Darkness can be camouflage

In dim midwater, avoiding a detectable silhouette is critical. Red or black skin helps an animal blend into the background when viewed by predators or prey using the available blue-green light.

Some animals combine red external tissue with a red stomach lining that hides the glow of recently eaten bioluminescent prey.

Not every red animal lives at the same depth

Ocean color patterns shift gradually. Near the surface, blue and silver countershading is common. Deeper, transparency becomes useful. Farther down, red and black bodies become more common.

These are broad patterns, not rigid rules. Habitat, behavior and visual systems vary among species.

ROV lights reveal colors the animal does not normally display

A remotely operated vehicle carries bright white lights that include red wavelengths. The camera therefore records vivid crimson bodies that would look nearly black under natural deep-sea illumination.

That is why expedition footage can show an apparently bright animal in an environment where the color functions as concealment.

At a glance

Frequently asked questions