def potential_cloud_shadow_layer(nir, swir1, water):
    """Find low NIR/SWIR1 that is not classified as water

    This differs from the Zhu Woodcock algorithm
    but produces decent results without requiring a flood-fill

    Parameters
    ----------
    nir: ndarray
    swir1: ndarray
    water: ndarray

    Output
    ------
    ndarray
        boolean, potential cloud shadows
    """
    return (nir < 0.1) & (swir1 < 0.1) & ~water
