littlesparkvt (2707383) writes "Impact of Asteroid 2012 DA14 would hit the Earth with the force of 185 Hiroshima Bombs or 1700 Kilotons. The impact of Tunguska in 1908 destroyed an 830 mile radius, 2012 DA14 would have a similar blast area." Link to Original Source
I've never been canoeing before, but I imagine there must be just a few
simple heuristics you have to remember...
Yes, don't fall out, and don't hit rocks.