Which of the following is NOT one of the five domains of joint doctrine?

The five domains of joint doctrine encompass various operational environments that military forces engage in. These include land, air, maritime (which refers to water), space, and cyber. Each of these domains is critical for developing strategies and conducting operations effectively.

In this context, while land, air, and cyber are clearly specified domains, "water" is not considered a standalone domain within the joint doctrine. Instead, military operations conducted in aquatic environments typically fall under the maritime domain. Therefore, identifying "water" as an individual domain is incorrect. Understanding these distinctions is essential, as it reflects the structured approach to military strategy that encompasses all relevant operational environments, except for those that do not fit within the established framework.