As if the sight of a shark in open seas wasn’t sufficiently ominous, researchers in New Zealand have now discovered some that give off an otherworldly glow in the pitch-black depths. According to The Guardian, scientists have discovered that three types of deep-sea shark can glow in the dark—including the kitefin shark, which can grow to six feet long, making it the largest-known luminous vertebrate. Researchers have fittingly described it as a “giant luminous shark.” The sharks all live so deep in the sea that sunlight doesn’t reach them, but their underbellies are lit up by the process of bioluminescence, when visible light is produced by a chemical reaction in living organisms. Researchers have suggested the sharks’ lit-up underbellies could help disguise them from any predatory threats that could attack them from beneath.