You might want to post this question in the Mid Atlantic Bottom Feeders forum because Maryland is considered Southeast US. I'll try to help you as best I can..
First, just to clear the air, Maryland is, was, and always will be considered the Mid Atlantic. Would post links but I can't yet.
Second, as others have indicated, Ocean City really is the only true good dive around here. That said, we have done the aquarium dive in Baltimore and, although expensive (I think it was close to $300), we felt it was worth it. First, you get a speciality (if you're a collector or working towards your Master Diver status you might like that). Second, it was a very unique experience. They provide (and insist on) all the gear so it would be good for somebody who is traveling. You do have to do a hour + brief in advance an interacting with stuff so that is to be considered.
You do two dives, one in a shallow (6 feet or so) ray tank filled with rays, a turtle, a nurse shark, and some other critters. During this dive you get to wave at all the kids staring at you through the glass and they get all excited (that was cute). Second you dive in a 15-20 foot circular tropical tank with all kind of small fish and a few morays. The fish love to have you dump rocks and they swim through them. Also unique.
If you do chose to do it, when we did it we had to book way early. It was run, and I think still is, by Atlantic Edge her in Maryland.