It might sound surprising, but in Montreal you can go surfing without waiting for the right wave. The waves here appear non stop because of underwater boulders, and they don't push you back to the shore.
Habitat 67 is probably the most easily accessible surfing destination in Montreal where you can ride the waves for the whole summer.
River surfing has plenty of differences with the ocean, but it doesn't mean it's easier as it also requires lots of preparation and concentration. Also, consider that during the season this activity becomes really popular, so you might wait in a line with other surfers. To avoid the queue choose the early morning or evening, which offers another advantage of watching an incredible sunrise or sunset.