19 U.S.C. § 1456

The compensation of any inspector or other customs officer, stationed on any vessel or vehicle while proceeding from one port to another and returning therefrom, shall be reimbursed to the Government by the master or owner of such vessel, together with the actual expense of such inspector or customs officer for subsistence, or in lieu of such expenses such vessel or vehicle may furnish such inspector or customs officer, the accommodations usually supplied to passengers.