The plants and animals that live in the rocky intertidal habitat must be able to withstand pounding waves and when the tide is out, hours of dryness. The rocks create a fairly stable foundation for the seaweeds and animals that have evolved to depend on this seemingly harsh environment. During low tide, small pools form between the rocks. Here, organisms like crabs, snails, mussels and barnacles are able to thrive. There are also many kinds of seaweed. When the tide comes in, larger animals like fish and lobsters are able to take advantage of the shelter and food these rocky settings provide.

Although the Massachusetts coastline is fairly extensive, there is relatively little rocky intertidal habitat. All of it is concentrated in the northeastern portion of the state. Ancient, underlying bedrock modified by millions of years of erosion and modified by glaciers provide the substrate. In this case, the bedrock is granite.