You guys just about have me talked out of using treated lumber.

I'm going to build a floating dock about 8' wide and 30' long. It will probably be made from 2x12, 2x6, and 1x6 lumber. What's the best commonly found lumber to use? Cedar? Redwood? How about the composite stuff used to build decks?

I am hoping to find somewhat affordable stainless steel fasteners. I'm afraid galvanized nails/screws/bolts would rust through after 5-6 years.

Thoughts?