blue water Navy noun an ocean-going military vessel US Coined well before the American invasion of Vietnam, when the term became widely used.
The desire to assert a global role through a “blue water” navy. — Rand Corporation, RandReport, p. 45, 1948
The U.S. Navy’s riverine forces were commonly referred to as the “Brown Water” Navy in contrast to the Blue Water forces[.] — T. L. Bosiljevac, SEALs, p. 51, 1990