There’s a jellyfish that can produce its own light
It's called an Atolla Jellyfish, but it's also known as the 'alarm jellyfish'. When attacked, it will launch a series of flashes, whose function is to draw predators who will be more interested in the attacker than itself. It's also a call for help. There are many other organisms that produce light.
97% of deep-sea marine animals have bioluminescent properties. Most of these marine animals produce blue and green light spectrums, the wavelengths that are most easily transmitted in sea water. The light is caused by a chemical reaction that releases energy in the form of light.