Scientists have found another Earth like planet far, far away and (possibly because they are morons) decide to try communicate with it. The aliens respond with an invasion. Thanks moronic scientists! Fortunately for us, the aliens have really, really slow ships that move like frogs which means the first third of the movie is spent making the main hero look like a douche bag asshole and does the job brilliantly. So well in fact, that you hope he dies slowly and miserably when the aliens do come, which involves some very nice CGI. It also turns into a somewhat decent action flick that tries to pay homage to both the navy and the battleship board game with an extended Liam Neeson cameo.
Given the ratio of water to land on this planet, that's not hard to imagine.
Unfortunately the aliens are stupid. They clearly have flaws in their technology which lets the modern standard of warships be on equal footing. For some reason they also can't decide if they want to kill people or not. That's a pretty big problem I would think? All the stuff with the scientists and ground based story line could have been compressed to just the army guy, and that whole opening part should have been removed because even after the movie is done - the hero is still a douche bag. All up I give this film two chicken burritos out of five, and don't have any desire to see it again.