LOL! The crabs aren't all that big - most of them are pretty little but still, there are a LOT of them. One of our family's favorite things to do at PINS is go out at night with flashlights crab hunting. We don't keep them, just look at them, play with them a little - like getting on one side to try and make them run in a certain direction.
They run sideways and if you aren't paying attention, they could run right into you. I think the biggest ones we've ever seen are maybe the size of a fist, but usually they are only half that big or even smaller. Because they are white and the sand is very light, it's hard to see them sometimes. Bring lots of flashlights!