Abstract: A device for protecting a hull of a marine vessel includes a cover of water-impermeable material dimensioned to conform to at least a water-contacting portion of a hull of a marine vessel. The cover is removably affixable to the hull, a top edge of the cover extending about the hull in spaced relation above a water line. A drain is positioned so as to lie adjacent a bottom of the hull when the cover is in place on the hull. In use, fresh water is transported into a space between the cover and the hull so as to displace ambient water therefrom. The ambient water can exit the space via the drain, leaving the fresh water within the space as a protective “jacket.” The fresh water serves to prevent galvanic corrosion, pollutant damage, and barnacle encrustation.