Boats are made from fiber reinforced resins. The resin can be anything with good bonding that is reasonably stiff; polyesters and epoxies are common. The fibers include glass, carbon, Kevlar, and other HM materials.
But what if you want something tough, but more flexible, like the side of a car tire? The resin can now be something like polyurethane sealant
and the fibers can be acrylic
or polyester... which is something like a tire used to be. The resultant material can be anywhere between a bicycle tire and a heavy mud flap. It can stick out, like the kayak
skeg below, or be a bonded part, like a patch.
So what would be good boat
- Skegs on kayaks and dingies (some would row a lot better with one added).
- PE Water tank repair. Welding is better but harder to master. Not fuel tanks, but potable jerry cans. Sika 291 is NSF potable water rated.
- Odd mast boots. It could be removable if you isolated it from the mast and deck during lamination with a backing material, such as a thin rubber sheet.
- Sails, inflatables, and clothing. That's old news. It works.