Getting back to the whole Black Court Crossing Water bit: I came up with what I think is a really fun way to define and/or handle it, but it would put a fairly significant spin on the Black Court as a whole. There is, per the novels, some connection between the Black Court and Necromancy (part of why they are rotting corpses, etc). You can take it a tiny step further, though, and say that the Black Court are, in fact, each a self-sustaining Necromantic spell effect. They aren't vulnerable to Circle Traps and such like other spell effects because there is no link to sever as the energy source is contained within them (fueled by their bloody diets which carries magical energy like no other), but they WOULD be vulnerable to the way large bodies of water ground out active spell effects. This would let you scale it fairly easily and much larger so that it wouldn't be easy enough to abuse for your PC's. The idea is that they are animated by an ongoing affect, but that open/running water would wash away some of the energy sustaining them, by at least the degree that a Wizard's spells are weaken. They wouldn't have problems crossing small streams (or the sewers under the streets), but crossing large or swift-moving bodies would weaken or even destroy them. It would give them a much larger vulnerability to heavy rain and other naturally occurring forms of Deluge, however, depending on how harsh you interpreted the water-crossing weakness before.
This is not exactly how it is presented in the books (and I dont know Stoker well enough to say for that side) but it does not contradict anything that Im aware of, so I think it could make for an interesting twist of secret knowledge and whatnot
