We were on the beach this morning around 9am. We noticed lots of these little crab like things buried in the sand where the water washed ashore. They had little feelers or antennae that stuck above the sand and every once in a while several would come up to the surface of the sand and scoot out closer to the water and bury themselves back in the sand. They were maybe 2" long and white/gray in color. They weren't shaped flat like most crabs, instead they were more oval shaped. What are they...anyone know?