...and a Heartwarming Moment, to boot. What exactly are the creatures doing at the end, when they put on the light show and ignore the nearby humans? The movie drops hints throughout, most notably that the lights are to attract other creatures. It's a mating ritual.
This is foreshadowed when Sam returns to her room the night before the ferry ride, and she turns on the TV to a documentary discussing the mating habits of jellyfish.
At the end of the film, one of the soldiers in the unit coming to pick up Andrew and Sam is singing "Flight of the Valkyries". You think "Oh, good - that guy from the beginning survived!" Then you realize the first words of the movie were the last words of the movie, too - the attack at the beginning is just about to happen...
And while alluded to prior to their trip into the Zone, their conversation with the smugglers strongly implies that the American government's bombing of the creatures is what's causing hostilities, rather than the other way around.
