Choose either day or night to go on these 1½-hour kayaking tours of Kyunaka-gawa (actually a canal) way out east of Ryūgoku. It's a wonderful way to get an alternative view of the city, plus some light exercise. If there is just one person on the tour, add ¥1000 to the pricing.
The website has instructions on how to dress and where to meet for the tours. Guides speak basic English.