The lower region of a body of water including the bottom. The organisms that live in the benthic zones within water sources such as ocean and lakes are called benthos. Benthos are made up of extremely small organisms that are invisible to the naked eye. Such organisms include sea critters, crabs, squirts, corlas, worms, sponges, etc. Much of these benthic organisms are attached to the bottom and will remain so for eternity. The benthic boundary layer within the specific body of water is important because it influences the natural living matter that resides there. These organisms are so adapted to habitating the deep water pressure are unable to survive in the upper parts of water bodies. The water pressure that differentiates between the uppermost layers of the sea and the lowest are simply too great for the organisms to adapt to. Since light does not reach very deep in the sea, the energy sources relied upon and obtained by the benthic zones are from the organic substances from the uppermost layers that drifts down to the bottom.