10 More Infamous Movie Plot-Holes (Solved By Fans)
8. Why Were The Aliens Defeated By Water? - Signs
The Plot Hole:
If the invading alien creatures are advanced enough to have built complex technology that allows them to travel to Earth, why would they be stupid enough to stop off at a planet that's mostly comprised of their big weakness, water?
The Solution:
There's been a fan theory doing the rounds on Reddit for the better part of 15 years which so brilliantly ties this one up it's a genuine surprise that Shyamalan didn't think of it himself.
Originated by user ZorroMeansFox, the theory posits that the aliens aren't aliens at all - they're actually demons.
More to the point, the water in the Hess household - a house owned by a priest, remember - could be holy water, the creatures' inability to open closed doors is consistent with the mythological depiction of demons, and given the film's central theme of faith, it absolutely tracks that the Hess family would be terrorised by demonic tricksters.
Again, this one fits snugly enough that you couldn't really blame Shyamalan if he just pretended it was his intent all along.