The midlittoral zone is covered and uncovered twice a day
by the tides. Animals in this zone have adapted to being immersed
in air and sea water. Anemones close when the tide is out, keeping
in the moisture necessary for survival. Mussels close their shells
tightly "clam up" for the same purpose, and open to
feed as the tide brings in their food.
This zones upper level - mean high low water - is approximately
+2.5 feet. The lower level - mean low low water is approximately
0 feet. It is frequented by a host of organisms and animals.