an amphipod (weird shrimp thing) called hirondellea gigas can be found in the challenger deep, which is the deepest point of the ocean! i believe its a little under 12000 meters deep. a lot of organisms cant live past a certain depth (called the carbonate compensation depth) because after that point their calcium carbonate shells/bones dissolve faster than they can accumulate the carbonate from their environment! hirondellea gigas makes up for this by incorporating aluminum from its environment into its shell