The Georgian Bay on the west coast appears to be a bay off the sea, meaning that it is a salt water bay. Georgian Bay in Ontario is off lake Huron, and is a fresh water bay.
The peculiarity of Georgian Bay (in Ontario) is that it becomes very deep very near the shore. There is a cliff inside the bay, just off the shore. If you go say 10 or 15 feet into the bay from the shore, the depth suddenly drops to 100 or 120 feet, you essentially fall off a cliff.
That is why it was a convenient port for trading ships etc. in the old days, the ships could come right near the shore.