I lived in Moose Jaw quite a while back. Pretty slim pickings for whitewater. There’s Buffalo Pound, which is a glorified slough that the water is so full of algae you can’t see your toes when you feet are ankle deep. Its OK for windsurfing though as long as you wear ear plugs. Other than that, I bought a motocross bike. There’s a nice dirt track south of the base, past Old Wive’s lake.