That'a a very fine shed. Looks like the YC has Seine in its name.Correct, the river is the Seine and the club I'm looking for is on the Seine. Association Voile de l'Ailette is, I think, a lake club.
Here's a shot of part of the club. There's a clue on its name. Who will solve it first? Tillerman! All is not lost! Der Dude, you are so close!