There are several local quarries.
Lake Millbrook is the closest and you have experienced the visibilty there.
Lake Rawlings is the warmest and
Dutch Springs is the nicest. There are a couple of other ones like Bainbridge and Guppy Gulch, but they really aren't worth the extra drive from your location.
There is pretty good ocean diving within 3 to 4 hours from our area - Ocean City, MD or VA Beach and just a little farther north gets you to New Jersey diving. I have done both OC and VA Beach as day trips from Rockville, MD. This is not warm water diving and a good day has about 40ft of vis - 15-20ft would be more average. But it sure beats quarry diving. There are lots of good wrecks right off our shores. If you like low vis diving, there is also
the U-1105 - MD's very own shipwreck preserve, although it is an advanced dive and you'll want to be comfortable in no-vis diving before you try it. There is no need to go too far for ocean diving if you can take water temps in the mid to high 50s - which is warmer than most of the local quarries at depth anyway.
The shop with which I am affiliated does monthly trips to NC which has fabulous diving, but you need to be AOW to go on those trips with us as we stick to the offshore wrecks if conditions permit. That is almost always high vis warm water diving.
Anyway, as you can see, there are lots of diving opportunities in the area - there is a volunteer diving program at
the National Aquarium in Baltimoreand two local underwater archaeology groups,
the Maritime Archaeological and Historical Society and
The Institute for Maritime History.
Hope to see you in the water,
Jackie