There’s something that I’ve known in theory but only have gotten to view in practice since moving to an island: beach sand moves. It’s in different places at different times. It may vary depending on the time of year, or it may move in response to a storm.
The things that don’t move appear and disappear.
This rock, rather like a breaching whale, was peeking out from a rather thicker-than-usual bed of sand after some good sized wave work had happened overnight.