Did the youngndum thing years back. The Isle Royale trip I did with a friend was a portaging deal. The interior of the park is a maze of small water, but to save time, we paddled across large bay mouths in quite open water, miles across. It was glass smooth conditions, but there was no one around if things went bad. We both felt the water, I didn't but my buddy jumped in one of the shallows, came running out immediately in August.