The fact that it was shot in Thailand makes for a constantly wet, lush green, thick jungle environment. You can practically smell the mildew as the clothes rot off their bodies...

"The film won and was nominated for several awards in 2007. Among awards it was nominated for, were from the Independent Spirit Awards and the Golden Satellite Awards in the categories of Best Supporting Male, Best Supporting Actor, and Best Actor in a Drama. The film garnered a win for actor Christian Bale from the San Diego Film Critics Society in the category of Body of Work."

http://en.m.wikipedia.org/wiki/Rescue_Dawn