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Sunlight doesn't penetrate ocean water below 3,300 feet. At 12,500 feet deep, the Titanic lies in what's known as the undersea "midnight zone." Even with the floodlights of submersibles ...

The ocean's twilight zone is a vast and dim layer that lies between the sunlit surface waters and the ocean's permanently dark, midnight zone. Also known as the midwater, or mesopelagic layer ...

below the ocean surface and sustains life across our planet. It includes the twilight zone and the midnight zone, where strange and delicate animals thrive in the near absence of sunlight.