Tidemark

My dictionary gives three definitions for the word tidemark. 

It can be the line on a beach at the high water point, the scummy ring around the bath at the level the water reached, or a line on a person's body revealing they didn't have a bath and just washed the bits they thought would show.

I'd like to suggest a fourth – the patterns left on sand as the tide recedes. Don't you think this tidemark is beautiful?