So growing up, one of my favorite games of all time was Uncharted Waters: New Horizons on Sega Genesis. It was/is a great game that is completely open with 6 main story arcs and complete control over how to explore/conquer/trade on the high seas.
Well the other day I actually find a copy for SNES, throw down $60 (a little high but I'm a sucker), and relive the best game of all time. I look it up one day online, and low and behold! Koei, the maker of said game, is still around in Japan! And they honestly only just this week released a free MMO sailing game! Uncharted Waters Online, which has been Japan only for years, is just now being released in the US!
I've only just started playing it, but it looks encouraging. The graphics are a bit behind the times, but going sailing looks and feels awesome. The tutorial/school beginning is just as slow and tedious as regular school, but I think I'm just about out of that and onto the high seas!
To get to the point, if you like games where you explore, trade, fight pirates, manage a ship, and have lots of strategy, give it a try! It would be great to have some other people to sail with! Take a look at: http://global.netmarble.com/uwo/ if you are interested.