You do not have to go to far from MD to get some awesome white water paddling in!! Great falls National Park up near DC is the place to go!! GO check it out but make sure you go with somebody who knows what they are doing or with an instructor!
Here is a shot of Jessie Benson taking it on!! Great shot Jessie
If your looking for an instructor call Scott Jorss of Potomac Paddle Sports and he will take care of ya