I went for a nice long swim in the Seine at Thomery a couple of years ago ... lucky its wide as there were some bloody big barges coming down it. No ill-effects but I was very careful not to swallow any water. The current was quite strong too. The owners of the gite told us they swam there but another local seeing me get out clearly thought I was a bit odd.
I also swam in the Loing somewhere a bit south of Moret-sur-Loing. There were nice shallows and obvious deeper bits, a nice bank to get in from, lots of locals swimming - seemed very clean and safe. It was next to a town but I'm not sure which one as I'd got there by kayak rather than road. We hired the kayak from a place in Moret; makes a nice day but would they still be open in the autumn?
