The Sunlight Zone
Light enough for photosynthesis. It is only a thin skin on the ocean, yet it holds most of the sea life people ever see.
The Twilight Zone
Sunlight fades to a faint blue, then to nothing. Many animals here make their own light, and many rise toward the surface each night to feed.
The Midnight Zone
No sunlight reaches this deep. The water hovers around 4 °C, and the only light is made by living things.
The Abyssal Zone
Near-freezing, pitch-black water above vast plains of soft sediment. The pressure is hundreds of times greater than at the surface.
The Hadal Zone
Named for Hades, the Greek underworld. Depths like these exist only in ocean trenches, most of them around the rim of the Pacific.