Krew.io is a fantastic 3D cannon fire game set on the high seas. You begin on one of two squads, denoted by colors, and control a ship with a cannon that goes around smashing other ships. This game is a lot of fun to play with friends or even by yourself because you can dismantle a fleet by yourself if you're talented enough. However, there are several AIs cruising the sea as well, and they are in large pirate ships that need your team to work together to take down!
Shift your cannon around on the boat with the WASD keys to steer it in the direction you want to go, and use the mouse to guide your boat/aim your cannon.
How to play:
To be competitive in Krew.io, you'll need to practice navigating a lot. When I first got on, the controls seemed strange because you switch your cannon around the boat to direct it, which clearly affects where you fire from, so you'll need to adapt before attacking. Teamwork is essential on the oceans, after all, a captain is just as effective as his crew. On that note, there are elected captains for teams, it will be arbitrarily selected and substituted once the captain dies, as far as I know it doesn't offer you any other perks other than the ability to issue orders in talk.