This product is much better for boat gelcoat than any automotive polish or compound I have used.  I give my boat a thorough waxing every year.  I have used varying levels of automotive compound before waxing to get the colors bright and remove water stains.  I used this Meguiar's Marine polish last year for the first time and I can tell a big difference.  My boat finish was shinier and the colors stayed bright all season, with no water stains.