Looking for a game that's similar to AC4 Black Flags naval/ship portion. Doesn't have to be pirate, could be future. I just like sailing, managing my ship and fighting other ships/forts.

Edit: spaceships are also cool.

I really like the sailing portion of black flag and find the assassin bit really only as that stuff I do when im not sailing.

Is there any game similar to the naval bit of managing a ship, fighting with it, sailing it, and trade/upgrades?

I tried searching it, but didn't really find much.