Did you know that the mirror coatings on your lenses are actually made of metal? This makes your lenses, as well as the metal pieces on your sunglasses, susceptible to damage caused by salt water.
The combination of moisture, oxygen, and salt (especially sodium chloride) is more damaging to metal than rust. This combination corrodes, or eats away, at the metal -- weakening it and causing it to fall apart.
Salt water corrodes metal five times faster than fresh water does. Salty, humid ocean air causes metal to corrode 10 times faster than air with a normal amount of humidity.
We always recommend running your sunglasses under clean, fresh water to remove any salt as soon as possible after a day on the water. This helps keep your sunglasses and lenses in top condition.