Joules is your captain - he runs all the boat tours in Chinon. The Vienne has pockets of quite strong currents, so taking a boat out on your own and navigating the Vienne is not an option. There are different packages and choices available, depending on how many you are/whether or not you want to be with other people/what season it is. Here is Julien’s board of scheduled departures, as well as his contact number (+33 06 76 74 51 14). He offers a charcuterie board and local wine if you request it in advance (at an understandable extra charge). The tourist office also know his schedule.