def _is_water_file(f):
    """
    Is this the filename of a water file?
    :type f: str
    :rtype: bool

    >>> _is_water_file('LS7_ETM_WATER_144_-037_2007-11-09T23-59-30.500467.tif')
    True
    >>> _is_water_file('createWaterExtents_r3450_3752.log')
    False
    >>> _is_water_file('LC81130742014337LGN00_B1.tif')
    False
    >>> _is_water_file('LS8_OLITIRS_OTH_P51_GALPGS01-032_113_074_20141203')
    False
    >>> # We only currently care about the Tiffs:
    >>> _is_water_file('LS_WATER_150_-022_1987-05-27T23-23-00.443_2014-03-10T23-55-40.796.nc')
    False
    """
    return 'WATER' in f and f.endswith('.tif')