anglerfish

At 8,000 meters below the Pacific surface, pressure exceeds 800 atmospheres — enough to crush a submarine hull — and no sunlight has penetrated for geological eons. Yet animals live there, and not just survive: they thrive in communities as dense and diverse as any shallow reef. The hadal zone is where life tests what it can endure, and the answers have rewritten basic biology.

Below 200 meters, there is no sunlight — yet roughly 76% of deep-sea animals produce their own light. The deep ocean is full of living lanterns.