Hi, Doug. I would check out two relatively new products. The first is Trex, a man-made wood resin blend. The second is a wood now being imported called Pau Lope. I saw samples of the Pau Lope and it is really something. It is so heavy that it does not float.
As far as railing designs, I would look at a book or two on decks for this. I'm sure that your library or home center. There are a lot of really neat designs that people have come up with but seeing drawings or pictures makes visualizing a lot easier on both of us.