Benthos
The organisms living at the bottom of the ocean are collectively referred to as benthos. The benthos are found in the lowest layer of a sea or river known as benthic zone. Benthos can be classified into three groups based on their habitat. The groups are hyperbenthos (organisms that live near the bottom. An example is rock cods), epibenthos (organisms that are attached to the floor or rocks. An example is sponges) and endobenthos (organisms that live within the sediments. An example is sand dollar).