PA/NJ/DE/MD CGs with sites right on a lake or shoreline

Janes Island State Park in MD has a few on the Bay.

Elk Neck State Park in MD has a few on the bay. Campsite photos

Point Lookout State Park has a few on a 'lake' that feeds into the Potomac and has access to the Bay on the other side.

If you are willing to head further south, North Bend COE and other campgrounds around Kerr Reservoir are excellent Campsite photos