I work for Pamlico Sea Base ( http://pamlicoseabase.org ) as a sea kayaking guide. One of our trailers is built for canoes and doesn't have fenders over the tires. Unfortunately someone wasn't paying attention when loading it with kayaks and the sides of a few boats sat on the tire for a 2 hour trip. We now have 3 boats with gaping holes in them.
It isn't very likely that you'll have a kayak with such a large hole, but whatever the size, here's how to fix it.
Step 1: Materials and Tools
1. some sort of patch. we had an old trashed boat we could cut up. The only other plastic I know that will stick well are those big blue 50 gallon drum/barrels. Make sure you wash it out well!
3. heat gun (I used a blow torch which isn't great but works)
4. a water bottle (for safety reasons)
5. a large metal spoon or putty knife
6. a pair of pliers