That's funny, I was just thinking about making a small pond out of an old canoe myself. Mine is an old Coleman canoe that's been down the river too many times and has a few thin spots from scraping over too many rocks.It's made of Polyethylene so finding anything like an epoxy to stick to it well enough to plug a leak for long probably aint gonna happen. Welding is the answer. I have carved small strips of plastic off the edge of the seats and melted them over the cracks and sealed the leaks while on the river. I used a propane bottle with a single burner stove attached for the heat source. It was a crude way to weld, but it worked well enough to get the job done on the river. I still don't have a plastic welder but I was thinking about using a soldering gun for a heat source and welding up any spots that look like they need it. The canoe could still be used for paddling around a lake, but it's river trips are over.
If your canoe is aluminum maybe you could find an epoxy that would seal small pinhole sized leaks. There probably is something that would stick and seal pinholes that you could spray on, like bedliner or some kind of liquid rubber, but I bet it wouldn't be cheap. What is your canoe made of?
(joking) Hopefully someone who knows about this will chime in though. Good luck!
