If you can gain access to the top and the bottom of the rivet. If the rivet is just loose. You can reset said rivet by having someone hold a peice of steel on the butt of the rivet, and whack the head a couple of times with a ball peen hammer. Or you could order a rivet set and a gun and reshoot the rivet.
Here's a link for all the riveting tools you will need.
Welcome To The Yard
I have brought old aluminum boats back to life that had 2' of their side taken out by a stump or a rock. It was a job, but in the end, had a much stronger boat.