Have you ever seen a seemingly empty seashell suddenly start moving along the sand? Or even more shockingly, discovered that a shell you’d recently found on the beach mysteriously changed locations on your counter?
If so, then you’ve probably witnessed a hermit crab in action. They live alone, within salvaged empty seashells, due to their own physical vulnerability. The crab is forced to peek outside the protective shell to move, and as the crab moves, so does the shell.