Wash. Rev. Code § 85.05.082
All the right, title and interest of the state of Washington in and to so much of the beds and shores of any navigable river, stream, waterway or watercourse located within the boundaries of any diking district up to and including the line of ordinary high tide in waters where the tide ebbs and flows, and up to and including the line of ordinary high water within the banks of all navigable rivers and lakes, to the extent that the same under any proceedings to be had under this act shall cease to become a part of such river, stream, waterway or watercourse by reason of the diversion of such river, stream, waterway or watercourse, under any proceedings had under this act, are hereby given, granted and vested in the respective diking districts now existing or hereafter to be formed; and the commissioners of such respective diking districts are hereby given the right, power and authority to sell such beds and shores in such manner and upon such notices and proceedings as govern, under existing laws of this state, the board of county commissioners in the sale and disposition of any real estate belonging to counties of this state. The proceeds of such sales are to be used for the benefits of such diking district in the payment of any expenses connected with the construction of such dikes or maintenance thereof: PROVIDED, HOWEVER, That the commissioners of such diking district may, in their discretion, exchange such abandoned beds and shores for other property needed in the straightening, deepening or widening of such rivers, watercourses or streams; and which exchange may be made upon such terms, conditions and in such areas as in the discretion of such commissioners they may deem advisable and for the best interests of such diking district, without any notice or other formality of proceedings whatever.
RCW 85.05.082