Montreal area beaches ( they are all small but crowded in the summer)
St Zotique( St Lawrence)
source:plage.st-zotique.com/
Oka ( Deux Montagnes Lake)
source: sepaq.com
St Thimothée ( St Lawrence)
source: plagevalleyfield.ca
Cap St-Jacques ( the only natural beach in Montreal, Deux Montagnes Lake)
source:
http://wpmedia.blogs.montrealgazette.com/
For the rest of Quebec, Magdalen Island has probably the nicest sand beach in Canada and the water temperature is not bad in July( 70 during the summer)
source: quebecmaritime.ca
source:
http://www.flickr.com/photos/snuffy/5960863146/