Crabs are a familiar crustacean. There are several species of crabs that can be found intertidally and subtidally along Maine's shore. True crabs are decapods, meaning they have 10 legs. These legs are located along the side of their body, causing them to move in classic crab motion, sideways. The legs at the front are generally armed with large pincers used to capture, crush, and feed on prey. Crabs do have tails but they are tucked up under the body. Crabs breathe using gills that are located under the carapace or body shell.

The rock crab, Cancer irroratus, pictured above is only common in the intertidal during the juvenile stage of development, prefering deeper, subtidal waters as adults. Both this species along with a similar crab, the Jonah crab or Cancer borealis are commercially harvested in Maine.