Why The Aliens In M. Night Shyamalan's Signs Make No Sense

Ask anyone to rank the best M. Night Shyamalan films, and there's a high chance that "Signs" will be somewhere in the top five, perhaps even taking the number one spot. It's understandable, really. Mel Gibson's search through corn fields and escape from his grief is still a nail-biting watch, with one highlight being Joaquin Phoenix recoiling from watching shaky cam footage of a kid's birthday party (which Shyamalan confessed to laughing at during filming). And yet, even with all those great moments, the one thing that "Signs" is remembered for the most is its final big reveal that also exposes its biggest plot hole.

Throughout the film, Rev. Graham Hess (Gibson) has been waiting for these space-based creatures to finally touch down on their home turf, which has been covered with half-full glasses of water thanks to his daughter, Bo (Abigail Breslin). It's only by revisiting the final moments with his wife and remembering her last wishes that he allows his brother Merrill (Phoenix, who was originally set to be played by Mark Ruffalo) to swing away, smashing containers of water all around the house when it's revealed to be toxic to the alien invaders.

It's one of Shyamalan's more notable twists that doesn't involve Bruce Willis, but one that stands out more than most for the wrong reasons. While it's commendable that the good reverend and his family have the proper defense to put the aliens on the back foot, should the intruders not have considered such an issue when visiting a planet that's over 70% water?

Imagine you're about to take over a planet inhabited by insignificant, lesser beings; getting an idea of the local terrain would be a smart move, right? Why, then, in the case of Shyamalan's creep-fest of UFOs and tin foil hats, do the aliens not factor in the poisonous wet stuff that not only covers the planet but often descends on the dry land in repeated intervals?

It's alluded to as the film progresses that the secret to sending the aliens packing lies in the water, especially when Shyamalan himself, cameoing as the killer of Graham's wife, Ray Reddy, reveals that he plans to take refuge by a lake. Being near a body of water might do the trick, but why wasn't it discovered sooner that the aliens don't like to get wet? Were there no reports from areas experiencing rainfall that the aliens were fleeing the scene? If they were confident enough to crash birthday parties, they surely would've taken a wander around, say, the U.K., for example, and as a result, most likely not survived the trip (they wouldn't have stood a chance in Scotland, that's for sure).

Even with this glaring issue, however, some fans have constructed their own theories as to why the aliens could have overlooked this, but just barely.

As is the case with any film-based conundrum, going online often solves as many problems as it creates. In the case of the black hole plot thread in "Signs," one theory posited that the water was dangerous not only for aliens but also for humans. Throughout the film, Bo is constantly asking for a fresh glass and stating that something is wrong with the water, leading up to them being stacked all over the house. A fan on Reddit suggested that the reason Bo (Abigail Breslin) kept changing glasses was because the water was, in fact, contaminated, and that while lethal to aliens, it had only a mild impact on humans.

The Redditor added that the water used at the Hess farm could've contained pesticides, which is why Bo always complained about it. The aliens attacking their home may also have been because it was away from large bodies of water, assuming that they'd be safe, only for that not to be the case.

Even with that explanation, the issue of aliens encountering rainfall or instances where someone else from Earth discovered this weakness and announced it to the world before communication went down remains unaddressed. With that in mind, perhaps the best option really is to just ignore this one issue in another otherwise suspenseful thriller.