A rolling stone gathers no moss.....

.... but a submerged log sure does. This mossy log is only visible at low tide but it must have been rolling around for quite a while by the look of the moss.

[Maggiemae]

One could just imagine it to be a huge island with rolling hills and valleys!

[Liana Bull]

@maggiemae That is exactly what I thought when I first saw it - might have to revisit when the tide is a little further in to give it that island look