When reaching the eastern shore of presumably Lake Ontario and being faced with this never-ending horizon what was that experience like? Was there a misunderstanding of it being another ocean, or did the native population provide the necessary guidance to navigate the great lakes? Did the native population have the technology to traverse the lakes, or did that come later with the colonials?
Indians knew the lakes were fresh water, 200 meters above sea level, and canoed along the edges for hundreds of kilometers. The early French explorers soon knew it as well. So by the time there were colonists, the extent and character of the Great Lakes was pretty well known.