green-water navy is capable of defense of its nation in depth and is a significant offensive force within its territory. Blue water The blue water environment extends from the outer edge of the green-water zone to the deep ocean of the world. A blue-water navy can project its nation's power throughout the world. The blue water policy was a long-standing political philosophy in Britain in the 18th century, which sought to advance British power through use of the Royal Navy, although the term "blue water" did not appear until 1834. See also Littoral zone References Oceanography