Answer: The deep-sea organisms found today have undergone evolution in the past and are very complex now because their body structure also varies from that of the organisms that are present at a lower depth.
The bodies of these organism does not contain any air cavities in which the pressure could exert. It is because of this, the organism are quite solid without any air in their bodies, thereby they can withstand extreme high pressure.
The organisms on the seafloor have do not have air inside their bodies. Unlike the hollow viscera of animals in the surface, the viscera of seafloor organisms are filled with fluid. Therefore, the internal and external pressure is equal and these organisms are not crushed.
