Right west of the 112 bridge, head north and turn right onto Richelieu. Park next to the falls and head for the park. Take off is right there. Ask locals for the best waves to catch.
This spot is not for beginners. First wave is a hard swim out and an even harder swim back. Second wave is more forgiving, but is pretty much always requires the use of a rope. In both cases, one must hurry back to shore so not to miss the exists. Failure to do probably won't kill you, but it will will guaranty a very long walk back and a few dings on your board.
Overview
Atmosphere
Beautiful park where you can watch others surf while relaxing. Friendly atmosphere among surfers. Occasional tensions with kayakers who tend to sit too long on the wave, but nothing to write home about.
General
Once you get your paddling action down and some experience under your belt (Habitat 67 for example), Chambly will take you to that next level. With challenge comes reward.