[Kaptlt.Endrass]

So, a nice little game I picked up (completely free) a few months ago. It's somewhat similar to Naval Action, but a lot more arcade-like. While you don't have players in open world, you do have multiplayer games where you can play 1v1 or 2v2 in player on player games, or 2v4 or 3v6 in cooperative play.

It recently came out on Steam as well (though I've never played it through there). Very interesting game, and it comes with a load of different ships...from minuscule 3-man sloops to 1st-rate ships that can carry well over 600 men. In my opinion, there's always plenty to do; be a pirate, and sink/capture British, French, Spanish, Dutch, Danish, and many other countries' ships, go into ports (as long as you have an acceptable reputation with the country that owns the port), or, if you're feeling cocky, go in and capture a port yourself.