As a boat building and repair material, cured epoxy resin is preferred for its versatility, durability, superior strength, exceptional moisture resistance, and chemical resistance—but not for its UV properties.
Most epoxy resin, on its own, is not UV resistant. Exposure to UV rays can cause an epoxied surface to yellow and degrade, so epoxy shouldn't be considered as a final finish surface if it'll be exposed directly to sunlight.
If UV protection is needed, the cured epoxy resin must be overcoated with a UV-stable coating such as varnish, clear coat, primer, or paint.