This was a ritual when we lived in Spain, and went for walks on the beach. Winston would find a rock that was just a bit too big for him to carry, drag it for a little way and then start to dig a hole for it, barking all the time. I always thought he was telling the rock off for being too awkward to carry :) I had to watch where I was standing, if I didn't want to be covered in sand. Happy memories!
(Scan from photo taken using Canon AE1 Program, May 2000)