The Collaborative International Dictionary of English v.0.48:
Benthal \Ben"thal\, a. [Gr. ? the depth of the sea.] Relating to the deepest zone or region of the ocean. [1913 Webster]WordNet (r) 3.0 (2006):
benthal adj 1: of or relating to or happening on the bottom under a body of water [syn: benthic, benthal, benthonic]