There are many more pieces of dockage, piers, buildings floating around the seas than wood from shipwrecks. All the storms and hurricanes, typhoons deposit more beams and planks into the ocean than all the shipwrecks, so unless the piece of wood has things like brass or copper fasteners, or other nautical clues it is really not possible to get a true ID on it. Waterlogged wood will always be dense and heavy even after drying for months or years, the salt permeates the wood and stays behind when the water evaporates. Amazingly flotsam even goes from ocean to ocean, so a piece of a dock shack from Tahiti has the possibility of ending up on your beach. Oh, and welcome to the site!! Hope you find a real treasure!!