There is a campground where I live Hampton, called Tidewater Campground, and it meets your requirements I believe...
It's right next to the estuary, across the street from the trestle where I fish almost everyday, and the boat launch is right down the tracks from the trestle, about .25 mile. You can launch in the estuary, and go right out to the harbor.
Its about 1 mile down Rte. 101 from the beach.
There is also another one in Hampton Falls that is real nice, and its down the street from the estuary too
http://www.wakedacampground.com