Quite a few in this area use pipe. If you can get it, white oak will last longer than red oak. Best yet if you live in a coastal area, you should be able to find a business that sells piling and timbers to dock builders and bulkheaders. Marine grade CCA treated lumber will still be there 50 years from now. That's the 2.5 lb/cf treatment, not the .4 or .6 lb/cf that used to be sold by the box stores. That's the stuff that scared the EPA who feared kid were chewing on playground equipment made from it. So the EPA decided to make it difficult for consumers to buy.
The marine grade has so much more arsenic forced into it, kids would probably get poisoned by it with one glance. You can tell by the dark greenish almost blackish color of the treated lumber that it's the marine grade.