Windward

Windward is an action-filled sandbox game that puts you in control of a ship sailing the high seas of a large procedurally-generated world.

Features:
- Large procedurally generated worlds for a unique experience every new campaign.
- Play with your friends via full cross-platform multiplayer! Bring your ship into your friends' worlds, or have them join yours.
- Play as much or as little as you like. The game saves your progress on the spot -- no need to save manually.
- Play it how you want: relax and immerse yourself doing trading and questing, or venture forth into pirate-infested lands for some high-adrenaline naval combat.
- Unlock new ships, find upgrades, recruit allies, fund new towns, build coastal defenses, even bribe pirates to join your cause!
- Extensive talent tree with role-specific specializations.
- Customize your ship to make it look how you want. Pink hull with black sails? Sure, why not!
- Procedural itemization system where higher difficulty automatically means better rewards.

Source: The Developer Website.