Benthos is the term that describes organisms that live on or in the ocean floor.
Benthos are the organisms that live on, in or near the ocean floor or other body of water. Benthos are classified into (i) microbenthos (organisms smaller than 0.1 mm including amoeba, bacteria, ciliates, and flagellates), (ii) meiobenthos (organisms between 0.1 and 1 mm in size including polychaetes, copepods, nematodes and turbellarians) and (iii) macrobenthos (organisms that are larger than 1mm including echinoderms, crustaceans, anthozoans and sponges).