The zone exposed to air only at its upper limit by the lowest spring tides, although almost continuous wave action on extremely exposed coasts may extend the upper limit high into the intertidal region. The sublittoral extends from the upper limit of the large kelps and includes, for practical purposes in nearshore areas, all depths below the littoral. Various subzones are recognised (based on Hiscock, 1985.) (Cf. 'subtidal'). Also "supratidal."

Of or relating to the subtidal zone which extends seawards from the MLWS tide mark and includes the sublittoral fringe

Sublittoral comes from the latin words "Sub" (Under) and "Littora" (Beach), referring to that part of the Earth's surface immediately below the intertidal zone and thus permanently covered with seawater.

of or relating to the region of the continental shelf (between the seashore and the edge of the continental shelf) or the marine organisms situated there

Under the shore.