When you are in Leeuwarden, one of the activities you can do is paddling. It is a mix of being sportive and touristic at the same time. It can be a good workout and you can see Leeuwarden through the canals.
You shouldn’t worry if you don’t know how to paddle. There are instructors that will teach you some basics from profesional paddling, so that you can stand on the paddle board without taking a swim in the water.