Primal

The film follows six friends on a field trip who set up camp in the remote wilderness of Australia. When one person takes a late night skinny dip in a nearby waterhole, she becomes incredibly feverish and agitated, and soon regresses to a crazed predatory state in which her companions suddenly become the hunted. When another begins the same beastly transition, terror descends on the remainder as they realize it's now kill or be killed.