Just off of RT 40 North of Baltimore is a small Chesapeake Bay park called "Mariner's Point" in Joppa (Joppatowne) MD. It is a waterside park in a cove area with access to some really nice Marsh paddling as well as access to the Chesapeake Bay - Gunpowder River area.
On this trip we chose to paddle around the immediate area and then go around the point into one of the branches of the Gunpowder River/Chesapeake Bay confluences.
The day started with dragging the Kayak to the launch area. If you visit here (and your Kayak is heavy as my tandem kayak is) I'd recommend that you forgo the Kayak launch and go straight to the boat ramp instead. The Canoe/Kayak launch is a stair-step approach best suited for light "single" Yak's unless you want a good pre-paddle workout :)
Once in the water though, the trip greatly improves. The area (once you round the point a short distance from the ramp) has a good Chesapeake Bay marsh feel, with plenty of Blue Heron's, the occasional Osprey or Bald Eagle and some of that "Capt. John Smith exploring the Chesapeake Bay feeling" as you paddle through salt marshes watching otters and turtles slip into the water on your approach.
We had the good fortune of a sunny day with one good "dumping downpour" (always fun on a hot day) and wishing the day would never end as the sun sets on the horizon. This area is worth a look if you are looking for a relaxing paddle destination.
A great afternoon or day trip.
Boat Ramp, Porta-Pots, Kayak Launch (needs some work but available)
From Rt 40 about 10 miles North of Baltimore (Close to I-95) Turn right on Joppafarm Rd. about 1 mile to right on Kearny Rd. then a half-mile to Mariner Point Park.