Five Layers of Darkness

Oceanographers divide the ocean into five vertical zones based on depth and light penetration. The epipelagic zone (0-200 m) is where sunlight reaches and photosynthesis happens. Below that, the mesopelagic or twilight zone (200-1,000 m) gets only faint, filtered light.

The bathypelagic zone (1,000-4,000 m) is pitch black. Pressure here is 300 times what you feel at the surface. The abyssal zone (4,000-6,000 m) covers most of the ocean floor at near-freezing temperatures. Finally, the hadal zone — named after Hades — plunges below 6,000 m into the deepest ocean trenches.