These aliens have invaded earth primarily because its rising water levels make it increasingly suitable for them. This is tied in directly to the game's use of resources. Water pumps litter the map and if they're broken open, water starts to spread at a rate that can be increased by fiendish unearthly technology (i.e. Space Pumps).
When in this more hospitable habitat, the aliens gain more power and can even regenerate. In fact, the four-legged beasts even take breaks to roll around in it, which makes them look just about as cute as a mobile tumor with teeth possibly can.
And this is where the game starts getting increasingly intriguing. The flooding is real flooding and the terrain and all the buildings are fully destructible. If you blow up a trench, you can control the flow of the water, and so the alien's area of power is reduced.
Water's freezing point is also modeled, so if you have a troop type with a cold-based weapon - such as the Ascension's Ice Hammer - you can turn it into solid land. Everything interacts according to basic, commonplace, real-world rules. If Maelstrom can live up to even a fraction of its potential, this could be one of the RTS highlights of the year.
