Bioluminescence lets many sea creatures glow, using light to attract prey or confuse predators.

The longer version

Light appears when an enzyme drives an oxidation reaction, a trick many unrelated groups evolved independently. Some animals keep glowing bacteria in dedicated organs and feed them through the bloodstream; others make their own chemistry. Uses vary with the situation.

A gentle shine tempts prey closer, a sudden flash startles a hunter, and a belly tuned to the faint downwelling light erases the silhouette seen from below. Signals also mark trails or announce readiness to mate. At depths where food is scarce, producing light costs remarkably little compared with the advantage it buys. As a result, glowing species are especially common in the dark layers of the open ocean.

Where this entry sits

Oceans and Sea Life looks at the salt water that covers most of the planet, from crashing waves and tides to the darkest deep-sea trenches. Expect notes on coral, fish, whales, sharks, jellyfish, shells, and the strange creatures that live far below the surface. The full list sits on the Oceans and Sea Life page, where every entry is listed in order.