Deep Sea Creature

At this depth, there is not enough light for photosynthesis to occur and not enough oxygen to support a fish living at higher levels. To survive, these creatures have much slower metabolisms and therefore can survive using little oxygen. They can also go months without food. Most food comes from either organic material that falls from above or from eating other creatures that have derived their food through the process of chemosynthesis (the process of changing chemical energy into food energy). Because of the sparse distributions of creatures, there is always at least some oxygen and food. Also, instead of using energy to search for food, these creatures use particular adaptations to ambush prey.
Hypoxic environment
Creatures that live in the sub-abyss require adaptations to cope with the naturally low oxygen levels.