1. Pertaining to the sea bed, river bed, or lake floor: The benthic ecological region of a large deep body of water is located at the lowest level which is covered with a sediment surface and some sub-surface sediments layers.
2. Referring to organisms living on or in sea or lake bottoms: Many creatures, termed benthos, thrive in the benthonic area including bacteria and fungi, as well as larger creatures like crustaceans and polychaetes.

Benthic also refers to the fauna living on the bottom, in contrast to the pelagic fauna, which live in the open oceans.
3. Etymology: A reference to benthos; from Greek, meaning "depth"; which designates the oceanic substratum.

In oceanography, of or relating to the deepest regions of the sea and the organisms inhabiting that environment: There was an article in Jim's newspaper reporting that a ship recently sank in the abyssal-benthic area of the Pacific Ocean near California and was completely inaccessible or unreachable.