A buddy of mine owned a house near Stingray Point in Deltaville for a few years. The tap water (from a well I assume) was pretty bad, barely drinkable. Soap would not make suds with it. Bathroom fixtures stained badly so it seemed like it had a lot of iron in it or maybe it is salts.
I am not sure what is in the water but the rumor seems to be that an asteroid hit the area quite a while ago (>50,000 years) which changed the ground water situation. I have no idea what the water is like at the marinas.
Great place to sail from though. The Rappahonack is one of the cleanest rivers in the estuary.
From what I've been told the water at most(all?) of the marinas (at least on Broad creek) have high sulphur and tannin contents. The tannins cause the staining and the sulphur stinks like a$$.
I can't say for sure why, but the water at Stingray, doesn't stink like it used to a couple of years ago. I'm told they installed a reverse osmosis filtration system, but whatever the change, it was most defintely welcome. I'd suggest running the shower as a check at the marinas you consider to see if the water smells like a$$. Its slightly unpleasant but we tolerated it, and the good news is it doesn't make you stink -- once you get out of the shower its fine. That said, my wife is something of a Trooper. A higher maintenance model might put their foot down. The water in the town doesn't have the problem.
People have different ways of dealing with the issue. I've seen at least one that have gone to the length of rigging massive tank/pump systems, so they don't put marina water in their tanks at all. Some fill their tanks from 5 gallon containers filled up for free at the Fire department. (There is a hose bibb behind the sign in front) Personally, I use marina water in my tanks for washing bodies and dishes, but don't really drink it. I keep milk jugs of water from home or the fire department in the fridge for consumption. Also, any time I'm visiting someplace that has good water I'll pump out the D'ville water and get a fresh fill.
Its just one of those things you get used to that makes Deltaville, Deltaville. We intended to move our boat closer to home, but are having a hard time thinking of leaving the friends we've made and it really is such a great sailing area with less traffic than further up the bay.