It is the purpose of this part, in providing for harbors and channels, that the appropriation made by the state be considered an advancement, and that the fees, taxes, and other revenues received under this part, to be credited to the waterways account, shall be applied against the advancement, until all advancements have been fully paid. Thereafter, all such fees, taxes, and revenues shall be available for continued expansion and development of harbors and connecting waterways. However, subject to the approval of the state administrative board, the necessary expense of administration of this part, and any expense necessary to the protection of the harbors, and connecting waterways, constructed or established under the provisions of this part, or any improvement to the harbors and connecting waterways necessary for the proper and adequate protecting of vessels, shall be paid from the fees, taxes, and revenues before being credited to the advancements. The state administrative board shall from time to time provide for the transfer of credits to advancements from the waterways account to the general fund, until the advancements have been fully paid.