I do fail to understand...your "argument"(?). I'm quite aware of what brackish water is. Salinity is a continuum of values from basically pure water to the saturation level of salt in water. I don't understand your clear split between brackish and marine, but not between brackish and fresh. If brackish is fresh, then how is the salinity of brackish close to the salinity of fresh? That's like saying I'm close to my own height.