Could there be a plausible way to have a freshwater river that sources water from a saltwater ocean? By plausible I mean by means of everyday, scientifically-sound, boring-ass reasons, so no magic.
I am not a scientist, and do not know anything about rivers. Please help.
This is actually an explanation I thought about; perhaps there's some sort of plant life that sucks up a lot of sodium and hangs around river-inlets? A mangrove tree is a great idea!