def _all_vertex_on_water(
    vert1_i, vert1_j,
    vert2_i, vert2_j,
    vert3_i, vert3_j,
    vert4_i, vert4_j,
    src_mask
    ):
    """Return false if any of the vertices is on land, true otherwise
    """
    if (
        src_mask[vert1_j][vert1_i] == 0
        ) or (
            src_mask[vert2_j][vert2_i] == 0
            ) or (
                src_mask[vert3_j][vert3_i] == 0
                ) or(
                    src_mask[vert4_j][vert4_i] == 0
                    ):
        return False
    return True