Remember, just because a bit of water won't drain out... doesn't mean a bunch of water won't squirt in from displacement loads. Boat is designed to take the load (water pressure) against the hull, not be filled with water.... but if you want to see how that seat brace separates from the hull...
We're talking an open floored tinny here... throw it in the lake, put some weight in it and sit and fish while you circle the leaking rivets with a sharpie marker. At the end of a long day throwing baits, take her home and reset the rivets that you marked. Repeat next weekend until you get them all, or you can just reset every rivet in the boat in an hour with the right tools.
When I bought the place up North it came with an early '60s Reynolds 12'r. It would have 3" of water in it by the time our daughter came back from work at Temagami Shores (gone for 7 hours). We put it on it's side against a tree, daughter inside with the bucking bar and me on the rivet setter. That was 10 years ago this June... it can now sit in the water for a month with ZERO water intrusion.