> It also (and this is most crucial "proof") explains the news over the radio at the end of the movie that an ancient method of killing the creatures has been found “in three small cities in the Middle East” –-which one would suspect are likely the religious “hubs” of the three main Abrahamic traditions, each discovering the “mystic methods” of protection-and-dispatch that I’ve noted earlier.

Even outside the religious framework, the radio provides a key bit of context that makes the aliens actions a bit more understandable for the "but why would they settle on a planet full of water!" folks.

The radio guest says that he believes the aliens weren't looking to conquer the planet; but rather, that they were there to "harvest" humans. The guest goes on to describe how other families were dragged away to the alien's ships, presumably to be used as slaves on their homeworld. Pretty grim bit of dialogue that's easy to miss.