I'm amazed that people would swim in the Seine. Someone once told me that it was so dirty that whenever firemen or police would jump in to save someone, they'd have to get a bunch of shots afterwards... maybe that was just an urban myth?
Hard to imagine, isn't it? That's why I wanted to see it for myself! I did see a short video on the Paris.fr website in which the swimmers reported that the water was fine. . .Maybe they've cleaned it up??