Descent
Take a breath. Below this line of light lies the largest habitat on Earth, and almost all of it is dark. Scroll, and we will sink together, one zone at a time.
Zone I · 0 – 200 m
The Epipelagic — the Sunlit Sea
This is the ocean most of us know: warm, blue, restless with light. Nearly every photosynthesising cell in the sea lives in this thin skin, which means most of the planet's oxygen is being made somewhere in the water around you right now.
Sardines school in silver shoals, turtles graze on drifting jellies, and mantas sweep through with mouths open. It is the busiest place in the ocean and also the shallowest: two hundred metres is barely the height of a tall office tower.
Zone II · 200 – 1 000 m
The Mesopelagic — the Twilight
Sunlight fades to a blue murmur and then to nothing. There is not enough light for plants, so everything here eats what falls from above or swims up to hunt at night. The largest migration on Earth happens every evening as billions of lanternfish rise toward the surface, and every dawn as they sink again.
Bodies grow strange: enormous eyes, mirrored sides, rows of photophores that erase their own shadows against the faint glow overhead.
Zone III · 1 000 – 4 000 m
The Bathypelagic — the Midnight
No sunlight has ever reached this water. The only light is the light living things make themselves: the blue-green flicker of a lure, the startle-flash of a squid, the slow pulse of a jelly's bell. Sperm whales dive to this depth on a single breath to hunt giant squid in complete blackness, navigating by sound.
The anglerfish waits with its lantern lit. Metabolisms slow to a crawl; some animals here may eat only a few times a year.
Zone IV · 4 000 – 6 000 m
The Abyssopelagic — the Abyss
The seafloor here is a plain that covers more than half of the Earth's surface, carpeted in a fine ooze of everything that has died above. Sea cucumbers, brittle stars and glass sponges sift through it with immense patience. Temperatures hover just above freezing.
Crimson jellies drift past; red is the first colour to vanish with depth, so down here it is the perfect camouflage. A marine snow of tiny particles falls constantly, the only weather.
Zone V · 6 000 – 10 935 m
The Hadal — the Trenches
Named for Hades, the hadal zone exists only in the deep trenches where one tectonic plate slides beneath another. The pressure exceeds a thousand atmospheres, enough to compress a polystyrene cup to the size of a thimble.
And still there is life. Pale, gelatinous snailfish glide over the sediment. Amphipods the size of a hand swarm anything that sinks. Bacteria in the mud break down the last remnants of what once swam in sunlight.
Challenger Deep · 10 935 m
The bottom of the world.
Only a handful of people have been here. Mount Everest, placed on this floor, would lie more than two kilometres beneath the waves.
It is cold, and it is dark, and it is quiet, and it is alive.