I've kept the water snakes that live in the wild in NY but only for a short time, I imagine many of the water snakes are similar... yes they are nasty. I had a 20 gallon tank with half land half water, all natural stuff from my backyard like dirt and moss and rocks and pond plants. I kept it in a shed outside with the door open during the day so it got natural lighting (I call it my nature shed where I keep things that I catch outside)... I would imagine it would appreciate a basking light. Since they are out and about during the day I think a UV light would be needed (as opposed to nocturnal snakes which dont really need one).

For any type of water snake I would say the bigger the tank the better. They love to spend time in the water but they also like to sit on land and bask or hide. Would be an awesome opportunity to make a really realistic looking tank. As for food, try different things and see what works. I've had some go for fish, I imagine they would also go for live rodents.

I've never kept mine more than a few weeks so I can't be of *too* much help, but good luck.