Firaxis has just unveiled Civilization: Beyond Earth's first expansion. It's called Rising Tide, and it will do pretty much what you might expect from that title. As with Civilization V's expansions, Rising Tide will add new systems on top of the existing game—in this instance, allowing you to colonise and mine the seas of the game's alien world.

In addition, Rising Tide will expand the role of diplomacy, and let players unlock new hybrid Affinity units and upgrades. You can see the list of key features below, via 2K's press release:

Building floating settlements and accessing natural resources hidden beneath the seas of the alien planet, while alien beasts with unique abilities inhabit the water and challenge players in distinctive ways

Shaping the diplomatic landscape by upgrading traits, changing diplomatic relationships, and leveraging the benefits of your allies, all with political capital

Unlocking a dynamic set of Diplomatic Traits while activating different combinations in response to the changing world

Playing as one of four new factions, including the Al Falah, a group of nomad explorers descended from wealthy and resilient Middle Eastern states

Investing in multiple Affinities to unlock hybrid Affinity units and upgrades for the first time;

Collecting and combining alien relics via a new Artifact System that unlocks powerful benefits

Exploring one of two new biomes, Primordial world, an untamed biome rife with volcanic activity and indicative of a chaotic landscape still forming in the new world

Civilization: Beyond Earth – Rising Tide is due out in Autumn, and will cost £20.