The benthic zone is one of the ecological regions of a body of water. It comprises the bottom—such as the ocean floor or the bottom of a lake—the sediment surface, and some sub-surface layers. Organisms living in this zone—that is, on or in the bottom of the body of water—are called benthos. The adjective benthic refers to something connected with or occurring on the bottom of a body of water. In contrast, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water-column up to the surface. More info on benthic zone from New World Encyclopedia.