We are having our backyard re-landscaped and the designer really likes the naturally distressed look of our deck. Over the years the paint or solid stain (can't remember which was used) on the deck has partially worn down to the bare wood. The deck is made of treated pine. If we do as the designer suggests and keeps the naturally distressed surface I believe the surface should at least have some sort of protector applied.

What should I use or do you have a different suggestion?