When I first saw that movie, that was my question as well. Wouldn't all the water vapor in the air cause their skins to constantly fizz, and their lungs to liquify in their bodies?

I think they missed a truly great way of handling it. I would have made the aliens have a bad reaction to alcohol- it isn't all around us, but it's certainly readily available. Then I would have had Mel Gibson's character be a heavy drinker since his wife died, and have him leave partial bottles of whisky or vodka or something sitting around for the big scene at the end. It would have been not only a lot neater in terms of taking care of that gaping plot hole, but it would have been a great way of having Mel turn away from booze.

I did like "The Village" a lot, though. Shymalian (sp?) does some nicely creepy work.