There are certainly some unique and interesting boathouses located on the Muskoka Lakes. These four boathouses are designed for sailboats and are found on Lake Rosseau in various locations. There may be others on Lake Muskoka and Joseph but these are the ones I have discovered running around by myself.
Located near the old Eatons property near Windermere on Lake Rosseau
Located on Ouno Island Lake Rosseau in Muskoka
Located at the top end of Lake Rosseau not far from the lighthouse