The native Americans in this are always had very bad feelings being around the Monongahela
which stands for Falling Banks and maybe the unstable cliffs along the river ,so maybe its a story they made up to scare people away from the river . But others thru the generations claim to have seen some kind of river monster either described as a large lizard or turtle some times with 2 heads and a long tail it uses to grab its prey. Or in the case of the Monongy a half human half fish .
What ever it is it has been supposedly spotted many times over the years the latest being this past summer when people claimed to have seen an alligator looking creature in the mon.
Talk to any Riverman and they will tell you beware of snakes on the deck and with good reason there have been many cases of people disapearing around the mon either by accidental drowning suicide or murder and on average 2-3 body's a month are pulled from the 3 rivers around Pittsburgh.
So is there a river monster ? maybe maybe not but when you see a strange mysterious object floating in the river always beware.