Best fish dives I've ever done where on the French River. If you are driving up to Manitoulin Island on Hwy 69 it would be at about the half way point. Site is called Recollet Falls, if u google French River you will see it just to the west of the Hwy. There is a trail on the south side of the river do able but would be a chore with scuba gear. We used to rent a boat from the marina on the east side of the Hwy thats about a 5 minute ride to the falls. Its not really a falls more of an elevation drop of 10/15'. Current is strong so a lot of grab and pull. You will see fish !!!!!! walleye, pike, bass, muskie and sturgeon and lots of them!
Not sure how active they are but the North Bay Scuba Club used to do club dives there every year maybe touch base with them for more info.