Last year Nintendo revealed that it was testing the free-to-play market with a sequel to its 3DS game Steel Diver, and today the game is finally launching. Dubbed Steel Diver: Sub Wars, the Nintendo 3DS game is free to download, but you'll only get a small amount of content if you don't splurge on the premium version. The initial download only comes with two subs to play as, for instance, while the premium version lets you use 18. You'll also get more missions and customization options by purchasing the full game — the free version essentially serves as a demo for the complete game, and there don't appear to be additional in-game purchases. Nintendo describes the game as a "tactical FPS" that features eight player underwater battles both online and locally. We're not sure on the pricing just yet, but the game will be available through the 3DS' e-shop later today.