Rare's Sea of Thieves is currently undergoing alpha testing with a select group of players. That pool is ever increasing though, so if you are part of the alpha, you'll have new content to play with following the recent 0.1.1 update.
In an update titled, Taming new Seas, players will have an expanded world to explore, with new islands to plunder and new dangers to avoid. There are skeletons of pirate past which will spring from the ground to threaten your crew, firing off old blunderbusses and trying to steal your hard earned treasure.
Players that are trying to steal your plunder will have a slightly harder time now, thanks to new anti-ganking mechanics, though you will still need to stay on your toes. Quite literally where possible, as Rare has now implemented fall damage, so no longer can you escape the clutches of your enemies by leaping to the deck of your ship from on high.
Sea of Thieves is expected to be released towards the end of the year for Windows PC and Xbox One.