FAQ for
Signs (2002)

You breathe oxygen all the time and you're OK. In fact you need it to live. However, oxygen is incredibly reactive. It corrodes most metal. It's explosive. And it can kill you, too. See: http://en.wikipedia.org/wiki/Oxygen_toxicity. It's all about concentrations.

You also breathe water vapor with no ill effects. However, many people drown every day. Inhaling large amounts of liquid water can also cause pneumonia which is potentially fatal. Again, It's all about concentrations.

The movie set up this plot point by explicitly stating that there was a theory that they didn't like water. Remember that they are ALIENS. Your rules don't apply, but there is ample precedent and foreshadowing for what is seen.

Water vapor may have affected the aliens, but this is not shown in the film. Liquid water is more concentrated than that of water vapor and was shown to have a significant negative affect to the skin. It can be assumed that as the relative humidity approached 100%, the aliens would be at greater risk.

HOWEVER, there is one point that people tend to overlook. Based on the radio report it is assumed that the aliens left behind were injured in some way. It can be argued that these were the aliens that were severely affected by water. The rest may have been able to tolerate small exposures.

Two reasons: What kind of environment did they come from? What are the rewards for coming to earth?

People live and thrive in inhospitable environments on earth all the time. The sea is very unforgiving, but sailors manage to survive. Deserts and the Arctic north are very nasty places to live but people are there as well.

The film implies that people are being harvested for food. That's as good a reason as any if food is scarce.

You can read religion into it. Each person will see it differently based on their personal experiences and biases. And it is this difference of interpretation that is a major theme of the movie itself.

This theme is that of faith. Faith can be religious or secular (self-determination). Some will see a priest receiving a message from his god. Others will see a man taking control of his destiny through a deeper understanding of life.

The central character is a Episcopalian priest that that has lost his faith due to a family tragedy. The events that he witnesses are sufficient to make him regain his faith. When experienced by a secular person, a different set of conclusions can be drawn. The events themselves are ambiguous.

It is this ambiguity that Night leaves with the viewer, showing that events sometimes can be seen as more than just coincidence. That they can be Signs. How you interpret them is personal. It is how individuals form their core beliefs.

Probably on their home world. The purpose of the crop circles is assumed to be navigation, but is left ambiguous. Maybe it's cosmic graffiti.

Remember, we are talking aliens here. If we understood them fully, we should be capable of interstellar travel. :)

They were armed. They had their "Alien Wrist Gas" (Whatever that is)

A hunter uses the appropriate weaponry for the prey. You don't hunt rabbits with a .357. You don't use an AK-47 on doves. You don't nuke bear. You use the just enough technology to kill so that you can make use of the carcass.

As for personal protection, If you're hunting for bear you bring big weapons In case things go bad. However, but if you are after small game you tend to not bother. The assumption can be made as a sufficiently advanced species capable of interstellar travel, they didn't see us as much of a challenge. Cocky doesn't have to be a uniquely human trait.