I think those are really powerful. I love 'public' art, and the idea of art that then gets swept away by the might of the sea is quite romantic and sad.
Reminds me of a story (by Ray Bradbury, I think - correct me if I'm wrong), about someone who witnesses a man drawing in the sand on a beach in Spain. The pictures are allegorical and beautiful. But then they get washed away by the sea.
The artist turns out to be Picasso . . .