My dad has a 41' yacht with a lot of exposed woodwork on it. He suggested using Sikkens Cetol Marine satin finish, which is a penetrating finish that is intended for external wood surfaces. It can be topcoated with a gloss finish and is easy to touch up if scuffed. It doesn't need to be sanded, either. It is fairly flexible and stands up to foot traffic well.
It costs $100/gallon, though. It is available at most marine stores. I'm going to try it on mine.
