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It’s one of those things that everyone recognizes, but no one really knows the name for: the quivering light cast by sunlight through waves that makes a netlike pattern on the bottom of lakes, oceans, or swimming pools. The phenomenon is called water caustics, and it may help some fish on coral reefs escape predators.
Reefs are hotbeds of biodiversity, which means lots of species and lots of hunting. Naturally, prey fish have developed diverse strategies to flee, fight, or freeze when faced with predators, and, with their study of caustics, researchers may have found one more. A recent study by Sam Matchette, a PhD candidate in biology at the University of Bristol in England, and others, indicates the phenomenon seems to obscure prey fish from predators, delaying attacks and buying prey precious seconds to get away. Here’s how some reef fish might use these wavering lines of light for protection.