Deep sea creatures employ bioluminescence for a remarkable variety of survival strategies adapted to the unique challenges of their extreme environment. Many predators, like the fearsome anglerfish, use light as bait, dangling glowing lures to attract curious prey within striking distance. Conversely, some prey species employ counterillumination—producing light on their undersides that matches the faint sunlight from above, effectively erasing their silhouettes when viewed from below by potential predators. Others use bioluminescent displays defensively, with the vampire squid ejecting glowing mucus clouds that distract predators during escape, while flashlight fish can rapidly blink their light organs to confuse pursuers. Social functions include the complex light patterns that firefly squid use to attract mates in the deep ocean. Perhaps most remarkably, some deepsea organisms can transfer their bioluminescent compounds to predators that attempt to consume them, essentially tagging their attackers with persistent glowing markers that make the predators themselves more visible to larger hunters—a sophisticated biological version of revenge from beyond the grave. Shutdown123