Hi Besalu, A couple of years ago a friend and me spent 3 days paddling stretches of the Canal du Midi on SUPs (overgrown surfboards you stand on and paddle) We started at the entrance from the Med near Narbonne (can't remember the name of the Etang where it starts off hand now ) and just paddled stretches here and there along the way towards Carcasonne. It was al pretty random realy we basicaly just drove along in our vans and picked spots where we could park near what looked like an interesting stretch, chucked the boards in and paddled for a few hours. It was pretty mellow and relaxed ! On one stretch we saw people in houseboats but generaly we just saw people jogging/cycling/walking their dogs along the footpath which runs along side the canal. If you want a relaxing few days I'd say it is a good choice. This website has a lot of good info
http://www.