see also green water navy
Green water refers to solid water breaking onto a ship, as opposed to precipitation, spray, or self-induced (i.e., by firefighting) collections. The term 'green' refers to sea water coming onto the deck taking a green colouring due to the presence of algae, which is masked by ambient light conditions (i.e., sky reflections) on the seas surface. Freeing ports and scuppers are fitted (and required) to prevent a rapid loss of stability. On some ships, a breakwater may be fitted to protect equipment and limit the aftward excursion of green water breaking over the bow, diverting the water overboard or through local freeing ports. Flare is added to the bow of a vessel to deflect water away from the decks. Additional bow height may also be added, either by increasing depth, increasing sheer, or adding a fo'c'sle deck/step. Although transient, green waters presents a large impact load, and as a result can cause damage to the vessel.