In Washington State, owners of waterfront property retain very few property rights re: the submerged portion of their parcels. The right to pay property taxes is the main right we keep. However, we do have the legal right to install and maintain one private mooring buoy per parcel. The buoy must be within a prescribed distance of the parcel, and meet very stringent DNR regulations re: design, construction, placement, etc. One may also apply for a DNR permit to install/maintain a private buoy, normally in an established mooring bay, near a community dock, etc. In addition to the installation rules, this type requires the payment of an initial fee, as well as annual fees for the right to maintain the moorage location. All installation/maintenance costs are borne by the applicant in all cases. I would definitely suggest asking first before using a private mooring for lots of reasons; there is no implied right to use another's mooring without permission. As mentioned here before, mooring installations vary in their design, installation, and level of maintenance. You could be risking your boat by hooking up to an inadequate mooring if the wind kicks up.