Whenever a river, lake, or other body of water is on the boundary line between two counties, the boards of county commissioners of the counties adjoining such stream or body of water may construct, purchase, equip, maintain, and operate a ferry across such river, lake, or other body of water, when such ferry connects the county roads or other public highways of their respective counties. All costs and expenses of constructing, purchasing, maintaining, and operating such ferry shall be paid by the two counties, each paying such proportion thereof as shall be agreed upon by the boards of county commissioners.