Underwater 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 chemosynthesis (the process changing chemical energy into food energy). Because the sparse distributions creatures, there is always at least some oxygen and food. Also, instead 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.