Which of these is considered a natural barrier in physical security?

A body of water is considered a natural barrier in physical security because it is a naturally occurring feature that can impede access or movement. Natural barriers are elements like rivers, lakes, or oceans that are not man-made and provide a significant obstacle to intruders. They can be advantageous in enhancing security by making it more difficult for unauthorized individuals to approach a facility or sensitive area.

In contrast, a building, fence, and guard post do not qualify as natural barriers since they are all human-made structures designed for specific security purposes. A building can serve as a barricade but lacks the inherent qualities of a natural feature. A fence provides a physical boundary but is an artificial construction. A guard post, while it functions as a security measure by monitoring and controlling access, is also man-made. Natural barriers like bodies of water benefit from stability and permanence that artificial barriers cannot replicate.