In Club Med, we spent our evenings scouring the beach for little hermit crabs. These little cuties start appearing on the sand beds every evening, as if on cue. Once you see one, you'll find alot more surfacing one by one. They come in all shapes and sizes (the shells I mean). Even the tinest ones have a little crab inside.
We made some videos but being a YouTube noob, I haven't figured out how to post it here. But you can click on this link to see the little ones scurrying around.