This photo is of the beach in Boulogne-sur-mer. Using the international language of bizarre pictograms it appears to be warning anyone who might be thinking of doing anything at all ever to just not do it.
Although it has to be said that the punishments should anyone attempt to walk their dog with a propeller whilst diving into the sea and driving a car/bike were not made clear. And there wasn’t anybody around who looked like they wanted to enforce any of these rules either.
Mostly people just ate ice cream and chilled their Sunday afternoon anyway. Thankfully, people don’t need signs to tell them how to do that.