There are many. You can use Google or Bing, they are there for a reason.
Don't make me google that for you
The best of them all is www.duckduckgo.com
Nerodia are very good pet snakes, but honestly, being around so many and having been around so many Cottonmouths, I don't see much resemblance at all. For me that is like saying that Pit Bull Terriers and Bullmastiffs look just alike. Nearly ALL non-venomous snakes will flatten their heads and puff up their bodies to some degree if they feel threatened, and Water Snakes aren't any more prone to doing that than Rat Snakes or Garters. The Hognoses, with their "Cobra" impersonation, are better candidates, although once tame they refuse to do the hooding thing. If you REALLY want a non-venomous that looks like a deadly venomous snakes, all the time, without even feeling threatened, AND you don't mind the very distinct possibility of being bitten, get a Viper Boa(Candoia aspera). These snakes are almost dead-ringers for the Death Adder(Acanthopis sp.), right down to that rather unique head/snout shape. Problem is, though, most of this species are not the most handleable of snakes, and are rather prone to biting. Once in awhile you will find a nice one, though. They also, like the White-Lipped Pythons that they share their home range with, need high humidity, so they really do well in sweater box enclosures or snake racks rather than an aquarium-type enclosure, and they tend to be secretive snakes, needing a hide box, not frequently out in the open, so if you want a display animal for people to look at, they're not a very good choice.