deep sea

Far beneath the ocean's surface is a mysterious world of cold temperatures, intense pressure, and almost total darkness. The deep sea remains largely unexplored and unknown to humans. Yet billions of creatures live in this vast, dark void. Many of these animals have bizarre adaptations that help them hunt for the limited food and survive in extreme conditions.

Definition: the vast, deep region of the ocean
Depths: from 200 meters below the surface to the
ocean floor
Conditions: dim light or total darkness, intense pressure, cold temperatures
Where: in all the oceans of the Earth
Inhabitants: billions of creatures, including carnivorous fish

Image credits: main image, Sean Murtha.