Wash. Rev. Code § 79.125.510
It is the duty of the department to survey the second-class shorelands and in platting the survey to designate for public use all of the shorelands as in the opinion of the department is available, convenient, or necessary to be selected for the use of the public as harbor areas, sites for slips, docks, wharves, warehouses, streets, avenues, parkways and boulevards, alleys, and other public purposes.
Upon the filing of the plat in the department's Olympia office, the title to all harbor areas so selected shall remain in the state, the title to all selections for streets, avenues, and alleys shall vest in any city or town within the corporate limits of which they are situated, otherwise in the county in which they are situated, the title to and control of any lands so selected and designated upon the plat for parkways and boulevard purposes shall, if the lands lie outside of the corporate limits of any city or town and if the lands form a part of the general parkway and boulevard system of a first-class city lie in the city, and the title to all selections for slips, docks, wharves, warehouses, and other public purposes shall vest in the port district if they are situated in a port district, otherwise in the county in which they are situated.
RCW 79.125.510