All vessels, whether sail, steam, or propelled by any other motive power, including vessels, barges, and rafts in tow, engaged in coastwise trade, including those engaged in trade or plying upon the navigable rivers of the State of Alabama, and all vessels exempt under the laws, rules, or regulations of the government of the United States shall be exempt from payment of any pilotage fee whatsoever and shall not be required to have the services of a bar pilot in crossing the outer bar of Mobile Bay or navigating the waters of the bay or other navigable waters of the State of Alabama.