Eric, in general I agree with you, but here in the Carolinas and much of the southeast, and particularly eastern North Carolina where the OP is, the rivers have a whole bunch of tannins in them from the cypress marshes adjoining them. Not to mention the odd pig farm run off or pulp processor. If you don't take prophylactic measures such as I suggested, an aggressive cleaning method is needed. Left unaddressed, some sort of acid based solution is required to remove the stain.
"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"