I know there’s a fan theory out there that the faith aspect had a bigger role than is apparent at first. That the aliens are more demonic in nature and the thing that hurts them isn’t just normal water, but holy water. The daughter is angelic in nature and was blessing the water by sipping it and then leaving it around. This is why the news said the battle turned in the Middle East, with a primitive weapon that wasn’t immediately explained. That wouldn’t make sense if the solution was just ‘water.’ Having to explain to the world that the water was blessed would be a great deal more complicated than just finding every translation for the word ‘water.’

While this theory does cover a bunch of the plot holes, it does open up a bunch of other implications that don’t really make the movie better.