Here are some Mid Atlantic waterfront options.
If you are okay with the Chesapeake Bay, one of the nicest beach campgrounds is Breezy Point. You literally back your camper onto the sand. You are 15-20 feet from the waters edge. It is gorgeous for early fall camping. Sitting by the campfire and listening to the water crashing 15 feet from you, amazing! No sewer hookups and I can't remember if they have a dump station or not. There is a nice bath house however.
The biggest downfall is NO PETS, so we haven't been in a couple years because of that. Great park though.
http://www.co.cal.md.us/Facilities/Facility/Details/15
Also consider Delaware Seashore State Park for Atlantic Ocean camping. Full disclosure, its about a 2-3 minute walk under a bridge to the ocean, but you are right on the Indian River Inlet for fishing or cool breezes. Full hookup campground with nice bathhouses, but no trees and not too many other amenities. Great location with easy access to Bethany Beach to the south, Dewey and Rehoboth Beaches to the north. We've been there 3 years now and its a yearly week long trip for us at this point! This upcoming year we will likely go TWICE its so nice. The beach access is clean and guarded on the south side of the park.
http://delawarestateparks.reserveamerica.com/camping/delaware-seashore-state-park/r/campgroundDetails.do?contractCode=DE&parkId=360109