Paris Plages stretches out from the Louvre to Pont Sully as well as around Bassin de la Villette, so you can literally be on the sand in the middle of Paris; they even moved the mini Eiffel Tower made of chairs to a spot near Pont Neuf.
Dances are held during the late afternoons, and the relatively small crowds on the sand are because the crowd is gathered around the music further to the back.
It was a relatively cool day, so people walking by got the fine spray of the misters meant to cool off beach goers on the wooden platforms.
I preferred strolling through the Jardin du Luxembourg with more natural beauty
even if some of the art is man made.
Now that it's August, it seems Parisians have all left for Les Vacances (vacation); it's not a bad thing to have plenty of seats to choose from in the metro :)