Maritime geography

[4] This distinction disappeared as increasing threats in coastal waters forced the amphibious ships further offshore, delivering assaults by helicopter and tiltrotor from over the horizon.

Rubel has proposed redefining green water as those areas of ocean which are too dangerous for high-value units, requiring offensive power to be dispersed into smaller vessels such as submarines that can use stealth and other characteristics to survive.

[2] Under his scheme brown water would be zones in which ocean-going units could not operate at all, including rivers, minefields, straits and other choke points.

The green water environment extends from the outer edge of the brown-water layer past any continental shelves, archipelagos and islands; perhaps a few hundred miles from shore.

The blue water environment extends from the outer edge of the green-water zone to the deep ocean of the world.