Most midwater animals have evolved an even more effective way to mask their silhouettes. Their bioluminescent photophores, found mostly on their undersides, produce light that breaks up the silhouette and helps the animal blend in with the background light filtering down from the surface. This adaptation, which functions in a similar manner to countershading, is called counterillumination.

The light produced by midwater animals is closely matched to the background light. Like the natural light at these depths, nearly all midwater bioluminescence is blue-green. Its interesting to know that many of these animals can control the brightness of the light they produce to match the brightness of the background.