In the tailraces below dams the water fluctuates a lot some days exposing the algae covered rocks and concrete.Have seen and took myself some bad spills. I had a gaff made from a 10/0 treble hook soldered to a copper pipe handle for landing catfish.I had it laying on the gunnel.I had the boat loaded but not quite all the way out of the slick stuff,I stepped on to it and as I was going down I grabbed the gunnel....right where that gaff was laying and drove one of those 10/0 hooks all the way in between two fingers.