VERTCRS["MLLW depth",
    VDATUM["Mean Lower Low Water"],
    CS[vertical,1],
        AXIS["depth (D)",down,
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Hydrography and nautical charting."],
        AREA["World."],
        BBOX[-90,-180,90,180]],
    ID["EPSG",5866]]