Between NJ and Delaware runs the Delaware River. As it runs south it empties into Delaware Bay. From that point the next stop is the Atlantic Ocean. There aren't many bike friendly ways to get across this body of water. Most either pay someone to cross one of the interstate highway bridges, or ride far to the north where small one and two lane country roads cross a much narrower river. To the extreme south is the Cape May- Lewes Ferry, which should be on everyone's list to do once. It conveniently connects a great little Jersey Shore town, Cape May, with the Delmarva Penincula. ON the Delaware side of the bay it connects just two miles north of a great state park with camping, Cape Henlopen.
All that said, there is a little known alternate route to the Delmarva that sits about ten miles south of the Delaware Memorial Bridge. It is Ft Mott State Park. Along with being a tidy little state park it happens to have a ferry that crosses the Delaware River. It's two part ride. Part A takes you to the Fort in the middle of the river. Part two takes you Delaware City DE. DE City is about 9 miles from Lums Pond State Park where there is camping. If traveling north and you need camping fac, Parvin State park in Nj is about 25 miles from FT Mott.
The Ferry is currently $11.00 and bikes are allowed. The sch'd is limited 3 crossings a day, so some forward planning is needed. lastly, a megatropolis of hotels, restaurants etc is about 10 miles from the park. So many options.
So, something to help your planning if you are riding up or down the East coast this summer.