Down in the deep ocean - below about 200 meters, where almost no sunlight can reach - the world is pitch dark. Or it would be, if it weren’t for the animals that live there. Scientists estimate that about 76% of deep-sea animals make their own light.
That makes the deep ocean one of the most bioluminescent environments on Earth. Lanternfish flash signals to find mates. Anglerfish dangle glowing lures to draw in prey. Squid blast clouds of glowing slime to confuse predators. Shrimp spit cocktails of light. Even tube worms and jellyfish glow.
Almost all the light is blue-green. That’s not a coincidence - blue-green wavelengths travel the furthest through water before fading. Every other color gets absorbed too quickly to be useful. So in the deep ocean, life chose its color carefully - and lit up the dark.
