The adhesive sealant is extremely strong, retains its strength above or below water line. Stays flexible too - allows for structural movement. Has excellent resistance to weathering & salt water. Stress caused by shock, vibration, swelling or shrinking is effectively absorbed. Check the bonding & sealing jobs this product can h? for you: fiberglass deck to fiberglass hull, wood to fiberglass, portholes & deck fittings, motors on fiberglass transoms, under mouldings.