The choice may vary based on weather conditions. Still, as a general rule, wearing a base layer underneath (the thickness of which will vary depending on outdoor and river water temperatures) and a long-sleeve fishing shirt for sun protection is advisable.
In colder weather, opt for waders that allow enough room for additional layers, like a warmer jacket. Although not worn beneath waders, wearing a brimmed hat and polarized sunglasses is always recommended for sun and glare protection while on the water.