Might it have been a true blue black snake?? I think they are also referred to as Milk snakes. But they are harmless to people. They eat rodents are are of no threat to people and not poisonous. I am pretty sure water moccasins have very distintive markings on them but I can't remember which ones. Plus I think they are poisonous. That would suck.

FYI - snakes are more afraid of you than you are of them. They will not attack unless they feel provoked.