Boatlife Life-Seal Silicone-Polyurethane Sealant Boatlife Life-Seal is a unique combination of marine silicone and polyurethane, formulated especially for fiberglass. LifeSeal offers a fast-curing, low odor, high adhesion, non-sagging, non-corrosive, non-yellowing formula. It provides a durable permanent watertight seal for joints subject to structural movement. May be used above and below the waterline. Use for sealing decks to hulls, thru-hull fittings, vinyl ports, sealingglazing windshields