VERTCRS["MSL depth (ft)",
    VDATUM["Mean Sea Level"],
    CS[vertical,1],
        AXIS["depth (D)",down,
            LENGTHUNIT["foot",0.3048]],
    USAGE[
        SCOPE["Hydrography, drilling."],
        AREA["World."],
        BBOX[-90,-180,90,180]],
    ID["EPSG",8051]]