Where did the sand go?

Today the level of the sand was about 10 feet lower than usual, we were able to walk over the rocks that aren’t exposed otherwise. As I was admiring the sight and walking in areas that I never imagined, I saw a couple of petrified logs, it feels amazing to touch them! I just imagine how many hundreds of years have been there :)
Another place I was very close to it’s a big rock (mini island) covered with mussels, I usually see it far into the ocean waves. Nature is spectacular!!