Bumps on hull.

I bought a Tahoe q5i bow rider from someone who had a dock and they would keep the boat in the water half the year. When I got home and cleaned the junk off the bottom I noticed the fiberglass had raised places all over. Blisters might be a more accurate description as far as size and shape but they are solid. My fingernail can’t deform the bump. The internet said it was from being in the water too long. I want to sell this boat and I want to accurately be able to let someone know about it and if it’s will get worse. I have had this boat 5 years and it hasn’t gotten worse but I only use it for a few hours about 4 times a year then store it in my garage.