The flashlight fish

The flashlight fish are a family, the Anomalopidae, of beryciform fish. There are some unrelated fish with similar features, some of which are also called flashlight fish. Notable among these are the deep sea lanternfish, of the family Myctophidae, of which there are over 200 species.
Flashlight fishes live in tropical waters across the world. Some species move to shallow waters or coral during the night, but otherwise, they are exclusively deep water fish. They are typically about 14 centimetres (5.5 in) in adult length, although some species reach twice this size. They feed on small crustaceans.

Flashlight fish are named for their large bioluminescent organs. These are located beneath the eyes and contain luminous bacteria. Two methods are used by different species for controlling light emission, either a shutter-like lid is raised over the organ or the organ is turned downward into a pouch. The light is used for predator avoidance, to attract prey, and for communication.