120 m
The twilight
Enough blue light to see a silhouette, not enough to grow with. Everything here is either a silhouette or a predator of silhouettes.
Cohort: hatchetfish, lanternfish, bristlemouth. Observed: 1,204.
Below two hundred metres there is not enough sunlight to be useful, so the ocean solved it differently: a hundred thousand species that make their own, and use it to hunt, to hide and to signal each other in a permanent night.
Follow the cursor down. The water gets colder, the pressure rises and the light changes from blue to the particular black that only exists where the sun never reaches.
Enough blue light to see a silhouette, not enough to grow with. Everything here is either a silhouette or a predator of silhouettes.
No sunlight at all. The only light is made by the animals themselves, and roughly three quarters of them make it.
Cold, dark, and full of falling food. The carbon that lands here takes centuries to arrive and is eaten within hours.
The largest habitat on the planet, and the least visited. Four hundred and fifty degrees of pressure and a permanent supply of marine snow.
Named for Hades, which is fair. Trenches make their own weather, and the animals in them have no reason to leave.
Most deep-sea light is blue-green, between 470 and 490 nanometres, because that is the colour that travels furthest through seawater. A red signal would be invisible at ten metres, so very few animals make one — and the ones that do are usually seen only in a fraction of a second by something that lives at that exact depth.