The river near our house almost never freezes, but a week of really cold weather and no wind allowed a glass smooth half inch thick layer of ice to form along the banks of the river. Down the central channel there was a clear area bout 30' wide.
I paddled down stream for about a mile and could hear the ice creaking and breaking from the displacement wake of the boat but did not think about it. When I turned around I found that my passage had broken up the ice, and the once clear channel was now full of floating ice being carried down stream by the current.
Heading back upstream against the flow of the ice chunks was one of the hardest paddles I have ever encountered. Between ice chunks building up under the boat, and my paddle catching on large pieces of ice I was seriously thinking about hopping out and portaging back across country. I finally did make it back to my take out spot.
It was a very warm day, (56) and I briefly though about not fully gearing up as I only intended to be out for several hours.
I am glad that I was dressed for immersion (dry suit) as a quick afternoon paddle could have turned out much differently.