Wash. Rev. Code § 79.125.500
In every case where the state of Washington had prior to June 13, 1913, sold to any purchaser from the state any second-class shorelands bordering upon navigable waters of this state by description where the water boundary of the purchased shorelands is not defined, the water boundary shall be the line of ordinary navigation in the water; and whenever the waters have been or shall be lowered by any action done or authorized either by the state of Washington or the United States, the water boundary shall be the line of ordinary navigation as the water boundary shall be found in the waters after the lowering, and there is granted and confirmed to every purchaser, the purchaser's heirs and assigns, all the lands. However, this section and RCW 79.125.510 shall not apply to the portions of the second-class shorelands which shall, as provided by RCW 79.125.510, be selected by the department for harbor areas, slips, docks, wharves, warehouses, streets, avenues, parkways and boulevards, alleys, or other public purposes. Further, all shorelands and the bed of Lake Washington from the southerly margin of the plat of Lake Washington shorelands southerly along the westerly shore of the lake to a line three hundred feet south of and parallel with the east and west center line of section 35, township 24 north, range 4 east, W.M., are reserved for public uses and are granted and donated to the city of Seattle for public park, parkway, and boulevard purposes, and as a part of its public park, parkway, and boulevard system and any diversion or attempted diversion of the lands so donated from such purposes shall cause the title to the lands to revert to the state.
RCW 79.125.500