Abstract: Described is a dewatering apparatus for insertion into and retrieval from an engine fuel tank through the tank inlet for removing water from the liquid fuel contained in the tank. The apparatus includes an elongate cylindrical container of fixed capacity and an elongate tie connected thereto and accessibly anchored near the fuel tank inlet. A volume of dry particulate hygroscopic material, principally cross-linked polyacrylamide co-polymer fills a minor portion of the container capacity, and is expandable to many times its dry volume in the presence of water without absorbing the liquid fuel, so as to remove water therefrom within the capacity of the container. The dry volume is selected to limit the fully expanded volume to within the capacity of the container.