We have barely begun to understand the mysteries of the ocean, yet humans have already inflicted considerable damage to marine life. Overfishing, plastic pollution, and ocean acidification are taking their toll on coral reefs and the creatures that depend on them.
The deep ocean, meanwhile, is home to a kaleidoscope of little-known sea creatures, from worms shaped like Christmas trees, to an octopus that can transform itself into facsimiles of other marine animals, to a light-emitting squid.
Here are just 10 of some of the most amazing animals that survive in the deepest depths of the ocean.
Read more about the fight to save the world’s oceans in our Blue Planet series.