3M marine adhesive sealant 5200 is extremely strong and retains its strength above or below water line. Stays flexible too - allows for structural movement. Has excellent resistance to weathering and salt water. Our sealant has excellent adhesion to wood, gelcoat, and fiberglass, forming a watertight, weather resistant seal which becomes tack-free in 48 hours, and cures completely 5 to 7 days.