Sand crabs are also known as ghost crabs because of their pale color and I think because they are so quick to duck down into their holes that they seem to disappear. They dig burrows in the sand up on the shore beyond all but the highest tides and mostly come out at dusk and at night. I have tracked them down by following the marks of their claws in the sand but they are almost impossible to catch because they can see you quite well with their eyes sticking up on stalks and because they are the road-runners of the crab world!
To me, ghost crabs look a little like large fiddler crabs, which also live in burrows but are found on mud flats of bays and estuaries. On the beach during the day, a ghost crab would likely end up a meal for a scavenging gull. They eat mole crabs, coquina clams, and dead fish, but are also said to sometimes raid the nests of turtles to eat the eggs.
It is good to know that my old friends, the sand crabs, are still flourishing on the same patch of sand where I played as a kid and I can show them to my children.