Ghost crabs (Ocypode quadrata) are common along the beaches of Hilton Head Island. This is a large (their shell can be 2 or more inches across), sand colored crab that is known for its speed (its name Ocypode means "swift footed"). Although it is most active at night, they can also be seen occasionally during the day, sitting at the entrance to burrows they build in the sand to escape predators and the heat of the day. Young crabs build these burrows closer to the ocean; older crabs build them higher on the beach. Even though they spend most of their time on land, ghost crabs breathe via gills, and must enter the ocean regularly to keep their gills moist in order for them to be able to absorb oxygen.
Ghost crabs eat many different things, including coquina clams and mole crabs, which they crush with their claws, but they also will eat dead animals and plants and the eggs and young of sea turtles. Raccoons are their main predator.
SC Department of Natural Resources: http://www.dnr.sc.gov/cwcs/pdf/Ghostcrab.pdf