Many intertidal organisms are confined to areas that remain relatively moist and cool at low tide.  The sea anemone Anthopleura elegantissima, for example, is commonly found in shallow pools or crevices.  At low tide they retract their tentacles and compress their soft bodies to conserve water. When submerged, anemones are subject to predation by the beautiful sea slug Aeolidia papillosa , which stores the stinging cells of the anemone (nematocysts) for use in the slugs' own self defense.  It is not known how the slug is able to consume nematocysts without being stung, or how it manages the transfer of stinging cells to its own tissue.

Soft bodied polychaete worms are also especially vulnerable to desiccation.  The soft parchment-like tubes secreted by sabellid worms are useful for protection from predators and desiccation. Sabellids anchor their tubes in rock crevices where they are protected from the rough surf. When exposed at low tide they retract their feeding structures into their tubes. Many other polychaetes take shelter in crevices or under the moist algae to prevent dehydration.

Sabellid worms retracted into their tubes at low tide

Katharina blends in well with its environment

Molluscs like snails and limpets use shells for protection from predators and environmental fluctuations. At low tide these animals can pull their shells down against the rocky surface. If pried loose by a hungry predator, snails will retreat completely into their shells and use the operculum to close the aperture and shut off access to the soft tissue.

Chitons can be difficult to spot in tidepools because they often blend in well with the rocks and algae. They are protected by calcareous plates that run down their backs and can also resist predation by clamping the mantle area around the shell down against the rocks. This makes it nearly impossible to pull the animal off of its substrate and has the added benefit of conserving water.

Bryozoans are soft-bodied sessile animals that can often be found encrusting on rocks or algae. To the naked eye, the colony looks like rough scales. Under the microscope one sees a crown of tentacles associated with each zooid, in addition to a calcareous outer skeleton.  Bryozoans can retract their polyps into their skeletons when they aren't feeding to protect the fragile polyps from desiccation and attack.

Pisaster starfish resting at low tide

The cobble area is subject to rough wave action and cobble tumbling, and consequently many of the animals found there have some type of tough exterior.  Animals in the cobble area, which is high in the intertidal zone, are also susceptible to desiccation.  There are some small pools under the rocks where most creatures are found, but the low diversity of algae indicates that the area is dry compared to the rocky promontory. Crustaceans and limpets are well represented in this area.

Porcelain crabs (genus Petrolisthes) are abundant under the cobbles. They cling tightly to the rocks and if harassed they are likely to autotomize (selectively release) a limb.  This remarkable ability helps the crab escape predation by freeing it from the predators grasp.  The limb will eventually regenerate during a subsequent molt.

The isopod Gnorimosphaeroma oregonense is also found in high numbers here. These crustaceans resemble the mottled terrestrial roly-polys to whom they are closely related. This isopod is found in aggregations under the cobbles and will roll up into a ball to protect the vulnerable underside when disturbed.  Idotea wosnesenskii is another isopod found under cobbles.  It's powerful jointed appendages allow it to grip tightly to the rock surface.

Stuck to the underside of many cobbles is a clump of wet sand that is, in fact, a tube containing a terebellid worm. Terebellids construct their tubes out of mucus and sand. The tube helps keep the worm moist, and keeps the worm securely underneath the rock.

Sweeping a net through the sandy shoreline will reveal a surprising number of small crustaceans, including mysids ("opossum shrimp") and cumaceans, which are closely related to isopods. These animals are protected by their sandy coloration and ability to burrow into the sand. There are also larger shrimp here of the genus Crangon, about the length of a little finger.  They are extremely well camouflaged against the sand, and are best seen after being caught in a dip net.