After the completion of the general study authorized by section 1222 of this title, the Secretary of the Interior, with the approval of the President, may enter into an agreement, containing such terms and conditions as are mutually acceptable, with any State or with a political subdivision or agency thereof (if the agreement with such subdivision or agency is first approved by the Governor of the State involved or by a State agency designated for that purpose) for the permanent management, development, and administration of any area, land, or interests therein within an estuary and adjacent lands which are owned or thereafter acquired by a State or by any political subdivision thereof: Provided, That, with the approval of the Governor of the State involved or of a State agency designated for that purpose, the Secretary may also enter into such an agreement for any particular area whenever the segment of the general study applicable to that area is completed subject to the provisions of subsections (a) and (b) of section 1222 of this title. Such agreement shall, among other things, provide that the State or a political subdivision or agency thereof and the Secretary shall share in an equitable manner in the cost of managing, administering, and developing such areas, and such development may include the construction, operation, installation, and maintenance of buildings, devices, structures, recreational facilities, access roads, and other improvements, and such agreement shall be subject to the availability of appropriations. State hunting and fishing laws and regulations shall be applicable to such areas to the extent they are now or hereafter applicable.