Geocache? This cliff face is on Carl Wilson Lake in Algonquin Provincial Park. Near the centre of the photo, you may notice that one of the pine trees has a white patch on it. Upon examining the tree through binoculars, it appears that there is a light blue bag hanging on the tree just below the white patch and positioned so that it would not be obvious when approached from the land side. The only reasonable explanation that comes to my mind is that this is a geocache.