Fibreglass boats are strong, and do not rust (iron oxide), corrode, or rot. They are, however susceptible to structural degradation from sunlight and extremes in temperature over their lifespan. Fibreglass provides structural strength, especially when long woven strands are laid, sometimes from bow to stern, and then soaked in epoxy or polyester resin to form the hull. Whether hand laid or built in a mould, Fibre-reinforced plastic (FRP) boats usually have an outer coating of gelcoat, which is a thin solid colored layer of polyester resin that adds no structural strength, but does create a smooth surface which can be buffed to a high shine and also acts as a protective layer against sunlight.
Boats or watercraft have also been made of materials such as foam or plastic, but most homebuilts today are built of plywood and either painted or covered with a layer of fibreglass and resin.