No need to trade sth, you´ll get the wine after a mini-quest from the barkeeper. Be sure to talk to the pirate before going back to the town.
I have gone back and forth between the town and the pirate a few times. The only thing that the lady at the bar tells me is that she has wine but she doesn't go any further than that.
Have you tried to read the way sign at the beach before talking to the pirate? (the one above the place where you see the underwater entrance) Did the pirate ask for the wine already ? Or do you know about the wine because of a hint on the forum or FAQ? It only works if the pirate asks for it. If you tried everything please contact our support email address.
No the pirate has not asked for the wine yet and I only know of it because of a hint I saw. I will try reading the sign and then talking to the pirate.