If someone says “You’re glowing!” you may be in love. Or, more likely, you’re a marine animal.

A whopping 76 percent of ocean animals are bioluminescent, which means they produce their own light through a series of chemical reactions or host bacteria that do. (Read more about luminous life in National Geographic magazine.)

It’s a separate process from biofluorescence, in which blue light hits the surface of an animal and is reemitted as a different color, usually orange, red, or green.

Marine creatures rely on bioluminescence for communication, finding prey, camouflage, and more. It’s so important, in fact, that the trait has evolved 27 times among ray-finned fishes, a huge group that makes up half of all vertebrate species