Blue-water navy is a shorthand term used to describe a navy that is capable of projecting national power at great distances across open oceans. Although there is no precise definition of the term, in contemporary times a "blue-water navy" has come to mean a navy that possesses one or more aircraft carriers.
The term is contrasted with a "green-water navy," which primarily conducts operations in and around its own coasts, and a "brown-water navy" which consists of small patrol boats and operates only on rivers and lakes.
Countries described as presently in possession of a "blue-water navy" include the United States, Great Britain, and France. Russia/the USSR is considered to have formerly operated a blue-water navy, but has since become a green-water navy. Countries considered to have "emerging" blue-water navies include China, India, and South Korea.