In 2014, marine biologist and National Geographic Emerging Explorer David Gruber was on a nighttime dive to observe biofluorescent corals when he noticed a bright green eel darting across. This was the first time biofluorescence had been witnessed in a vertebrate. Curious to see if there were more such creatures just waiting to be discovered, Gruber and his team began combing through coral reefs around the world. Sure enough, they found that 180 species of animals, including bony fishes, reptiles, and even the hawksbill sea turtle, have the capability to “glow” in the deep dark ocean waters.