I fixed a leaky riveted aluminum duck boat years ago by using JB weld on the bottom by coating the suspect leaky rivets with some overlap onto the bottom. I used a little sand paper to give it some texture to stick on to. I worked in batches to make sure the Jb weld could flow/seep into any cracks around the rivets. I did this to about 30 rivets. To my surprise it worked great and lasted for years. I was able to flip that boat over which made it easier. I think if you could get access to the rivets from underneath I think it would work. A pretty inexpensive option, might be worth a try. If using an aluminum welder make sure they are very experienced with aluminum welding on a boat. I once had a welder “blow” several holes in the bottom of an aluminum boat by mistake when he was doing some welding work on a boat I have. It ended up being a hole repair job which he was able to eventually do and the boat is leak free.
time spent fishing isn't deducted from ones life