Just stole this from the Virginia Dept of Game & Inland fisheries:
Wood and Hardware: Wood for piers should be pressure treated to retard decay. The most popular treatment is (CCA) treatment salt-treated. CCA treated wood is a good choice because its green appearance is widely accepted, it is less likely to stain clothes than wood treated with some of the other treatments, can be ordered with various amounts of treatment, and has a good record of holding up to the elements. CCA wood that will be in constant contact with saltwater, should be treated to a level of 2.5 pounds of retention per cubic foot (pcf) of wood. Wood that will receive saltwater splash should have a retention of 1.5 pcf. For fresh water, wood that will be continually exposed to water should have a retention of 1.5 pcf with wood above the water, having at least 0.6 pcf. All bolts and nails should be hot dipped galvanized. Where hardware will come in frequent contact with salt water, a better choice would be stainless steel since our experience is that even galvanized hardware will rust in time.
