Last year's Civilization: Beyond Earth was an interesting twist for the venerable strategy series: it took what has been a historical simulation and transformed it into a game about settlers surviving the new frontier of space. It featured giant sand worms, hypercomputers, and augmented humans. But for some, it just wasn't sci-fi enough. "One of the biggest criticisms that we got was that the game didn't go far enough, that there was a lot of potential for it to be even more audacious, more sci-fi, more different from the historical Civ games," says co-lead designer David McDonough.

The solution was out in the oceans.

Today developer Firaxis is announcing the first major expansion for Beyond Earth, called Rising Tide. And the big selling point is that you can finally venture from the land and start exploring the oceans of alien planets. You can even build new settlements right on top of the water. "Aquatic gameplay was a great opportunity to push the sci-fi," says McDonough, "and make the game different from its predecessor." With the oceans comes new aliens to deal with, new resources to harvest, and new naval units to add to your armies. The visual style has also been upgraded with some cool new transparency effects, so that you can see the creatures that lurk beneath the water's surface.

"It's what we like to think of as a Firaxis-style expansion," producer Andrew Frederiksen says of Rising Tide. "What that means to us is, not only are we adding some additional content, but we're also expanding and redefining some of the core experiences that you would expect from the base game." That includes additions not necessarily related to the new aquatic theme. The expansion will include four new factions to play as, including one made up of a fabulously wealthy group of Middle Eastern expats, as well as new types of planets to explore (called biomes in the game). The base game included three, and Rising Tide will add another two, including one described as a primordial planet "rife with volcanic activity and indicative of a chaotic landscape still forming in the new world."

According to McDonough, the majority of the new features were designed based on feedback from players. "The biggest ideas for this came from the day after the main game was released," he says, "and we really got a dialogue going with our fans." Those fans will be able to experience the changes for themselves later this year — Rising Tide will be launching on Windows this fall for $29.99.