Lantern fishes use bioluminescence to protect themselves from predators. By lighting their bodies, their silhouette is less visible from below.
Flashlight fish have special pouches of glowing bacteria under their eyes. When they want to turn on their lights, they lower folds of skin below each eye. By using a technique known as "blink and run," they can swim in one direction with their lights on, then quickly turn them off and swim in another direction. Eventually their predator gets disoriented and the flashlight fish escapes.