After your done with the Heartless on deck. There will be a cut scene showing Peter and Sora getting ready to trick Captain Hook. When the battle starts let Captain Hook have it. Now at some point in the battle Hook will either throw a exploding box at you or summon heartless to attack you, do not avoid the heartless, their annoying if you do. Take care of them then continue your fight with Hook. When you see that either you or your party are about to get K.O'ed. Fly out of Hooks reach and cure you and your party. Make sure you have at least two Mega-Elixers so you can replenish your health and magic repeat until Hook is thrown overboard.