Breezy Point campground in Calvert County MD is on (and I mean ON) the Chesapeake Bay. You park your RV on the sand about 30 feet from the bay. They are water/electric only. No sewer, no dump station, but they have honeypot service and decent bathrooms. No pets allowed either =(. It is a great campground though. The breeze off the water keeps bugs at bay. It gets a little chilly at night and nothing beats sitting by the campfire and listening to the waves crash against the shore 20 feet away. Highly recommend.
Raystown Lake in PA. I haven't been, but my buddy has been a couple times (Lake Raystown Resort campground) and we are going at the end of the month. Its situated right on the lake and has a lot of lakefront sites and a lot more lakeview sites. Prices range depending upon time of year and proximity to water. Sounds like a great time and I am looking forward to going! Water and electric sites, no sewer though. They do have a dump station and the bathhouses are pretty clean according to my friend.
Wife and I went to Otter Lake 2 years ago in the winter. It was God awful cold in the winter, I imagine its beautiful in the summer. Not a huge lake, but not small either. Its up in the Poconos, not much to do around the park though.
Just got back from 4th of July at Point Lookout... it is close to the water but no sites have direct access to the water unless you feel like forging your own path through bug, rodent and snake infested reed grass. Two loops have pier access where you can fish. It is a state park with a public beach at the furthest southern end of the park. Their were a ridiculous number of jellyfish in the water though. Standing on the pier at one point we counted 17 different jellyfish within view, and thats in the dirty Chesapeake Bay water. Sites are mostly electric only with water spigots placed throughout the park and a dump station. They have a few full hookups, but they are furthest from the water. My FIL loved it, the MIL, wife and I didn't care for it so much...
You've already tried Deleware Seashore Park, that would be my only other suggestion. Sites aren't terribly small, its directly on a canal between the Atlantic and 2 bays. It is essentially a parking lot though...
