A descent in ten thousand metres
Where Light Dies
The ocean covers 71% of this planet, and its average depth is about 3,700 metres. This page sinks from the sunlit surface to the deepest point ever measured — 10,935 metres down. Scroll to descend.
Scroll to descend
First, the scale
Seen from orbit, Earth is blue because the ocean covers 71% of its surface. The water below averages about 3,700 metres deep — the typical patch of ocean is midnight water stacked three kilometres high.
You are sinking now. The gauge on the right is your depth; every metre is real, measured water, and most of it has never been seen by human eyes.
I · 0–200 m
The sunlight zone
Almost everything you picture when you picture the ocean lives in the top 200 metres — and almost all of the ocean's light dies here.
Half the sunlight is absorbed in the first few metres. Red goes first, at about ten metres; then orange, then yellow. The deeper you sink, the bluer the world, because blue is the light water keeps the longest.
At about 100 metres, roughly one percent of the sunlight is left. The water looks empty, but it is snowing: dead plankton and dust drift down in a slow white fall that oceanographers call marine snow. It is the food of everything below.
At 200 metres the sunlight zone ends. Below this line there is too little light for photosynthesis: no plant and no alga can live on light down there. Everything deeper runs on food that falls from above — or on each other.
II · 200–1,000 m
The twilight zone
From 200 to 1,000 metres there is light to see by, if your eyes are big enough — but not light to live by. Eyes here grow enormous. Bodies turn black, silver, or transparent — and red, which in water without red light is the blackest black of all.
Sperm whales dive straight through this zone, past 1,000 metres, hunting in darkness by sound. Each one is a mammal holding its breath, listening for squid.
In 2004, at 900 metres deep off the Ogasawara Islands, a camera on a baited line took the first photographs of a living giant squid — after three years and 26 expeditions. Until that September night, the eight-armed, two-tentacled legend had never been seen alive.
At 1,000 metres the last sunlight gives out. Everything below this line is the deep sea — and the deep sea is most of the ocean: with an average depth of 3,700 metres, the typical column of water is over two and a half kilometres of permanent night.
III · 1,000–4,000 m
The midnight zone
No sunlight has ever reached this water. It is not empty, though — it is simply lit differently. Down here, light is something animals make.
Three quarters of the animals living between the surface and 4,000 metres can make their own light. Lures, camouflage, mating signals, burglar alarms made of sparks: in the midnight zone, bioluminescence is the rule, not the exception.
Flash your light
The water is watching. Send one pulse into the dark and see who flashes back.
At 3,800 metres lies the most famous shipwreck on Earth. Titanic sank on 15 April 1912 and was found on 1 September 1985 by a Woods Hole–IFREMER team led by Robert Ballard. No daylight reaches her decks: every photograph ever taken of her was lit by a submersible.
The water here is around 4°C, barely above freezing — and it stays that way all the way to the bottom. Heat, like light, is a memory of the surface.
IV · 4,000–6,000 m
The abyss
Below 4,000 metres begin the abyssal plains: among the flattest landscapes on Earth, built grain by grain from falling snow.
Every ten metres of water adds another atmosphere of pressure. At 5,000 metres you are under about 500 atmospheres — five hundred times the weight of the air on your shoulders right now.
At 6,000 metres the abyss ends. Below lie only the trenches: narrow cracks in the seafloor, holding the deepest water on the planet.
V · 6,000–10,935 m
The trench
The Mariana Trench, in the western Pacific, holds the Challenger Deep: 10,935 metres of water, the deepest point known in any ocean. You are entering the hadal zone — Earth's deepest habitat.
Mount Everest stands 8,848.86 metres above the sea. Sunk into this trench, its summit would still lie two kilometres underwater.
The first to touch this bottom: Jacques Piccard and Don Walsh, in the bathyscaphe Trieste, on 23 January 1960. The first solo: James Cameron, on 25 March 2012. The deepest of all: Victor Vescovo, starting 28 April 2019. All together, fewer than thirty people have ever been down here.
10,935 metres. Pressure: more than a thousand atmospheres. Light: none, except what you brought. And yet the mud is alive: amphipods, sea cucumbers and translucent snailfish farm the snow for food.
The light is still there
Ships have mapped only a few percent of the seafloor in detail; the rest is known the way the Moon's far side was once known — by gravity, by echo, by inference. You have just crossed it, ten thousand metres and more, without leaving your chair.
Scroll back up. The squid, the whales, the red light at ten metres — all of it is still there, stacked above you.