Ghost crabs, Ocypode , are common on beaches where they dig burrows in the sand and prey on other beach creatures. I have seen them taking turtle hatchlings into their burrows. Their eyes are unusual in that they can be raised vertically on their eyestalks or lowered into grooves of their carapace. Fiddler crabs , too, live in sandy areas. These small crabs gain their name from the huge pincer that the males have.
Hermit crabs are another interesting group.
They have a soft abdomen which they protect by living in abandoned gastropod shells. As they increase in size, they discard small shells for large ones. Crabs are among the most active of the intertidal organisms and barnacles the least so, yet they are closely related. Both share the characteristics of jointed limbs and tough external skeleton. Barnacles, though sedentary in the adult stage, have six pairs of feathery limbs which they extrude when covered by water and catch small organisms for food.