It’s not just water that can affect the look of your watch over time. Sweat, sun lotion & other liquids, as well as excessive sun exposure may also prematurely age it. Sweat, in particular, is corrosive, so if you repeatedly wear it during exercise, then some parts may develop a patina i.e. a unique aged finish. The inside part of your watch strap (where it comes into direct contact with the skin) may start to look as though it is flaking or it may become discoloured. So, do take it off before exercise.