During one revolution of the moon, two high tides and two low tides occur. The life-forms that survive here have adapted to considerable stresses, enough to discourage most organisms, yet complexities often spur biological molecules to adapt. Each living marine organism has adapted to a niche and developed strategies for survival. The prime requisite for the survival of rocky shore intertidal creatures is the ability to hold on in the face of surf action. Sea stars possess hundreds of tube feet for suction attachments to rocks.
Mussels secrete elastic byssal threads to secure their shells.
Different species, different approaches to the problem. When you walk toward the sea during a minus tide, notice how you pass through zones of different organisms that depend on how much time is air time. The first zone constitutes the spray area where organisms get showers only during the highest of water levels, and life is more a matter of air than water survival. Storm surges provide good growing conditions while dry summers stress living here. Black lichen, periwinkles, limpets, and acorn barnacles are found in this highest zone the penthouse apartment.