80% of all creatures who live underwater, below 1,500 feet, are luminous.
Bioluminescence, or the ability of an organism to create light, is one of nature’s most amazing phenomena, seemingly drawn more from science fiction than science and natural history. While relatively rare on land, bioluminescence is very common in the ocean, at least in the pelagic zone (the water column), where 80 percent of the animals that live between 200 and 1,000 meters (656 and 3,280 feet) depth are bioluminescent. Bioluminescence is most common among fish, squid, and what we call the gelatinous zooplankton – jellyfish, siphonophores, comb jellies, and other animals that are mostly made of water.