dark (esp. as to the ocean) adj.: aphotic
The depths [of the ocean] can be divided into three realms—sunlit, twilight and midnight where there is no light at all and temperatures are near freezing. The midnight zone, called the aphotic zone by oceanographers, makes up 90 percent of the ocean. It is the home of little-known creatures and blind fish that will never see day, never venture even into the twilight. (Linton Weeks, “Cosmic Relief,” Washington Post, 1/2/2000.)
