Gorgeous!
We go to Horseneck for a weekend each year. If you book early enough you can get a site along the beach. Either way you can hear the waves from all of the sites at night and they're all a short walk to the beach. The beach is a bit rocky but the water is blean and sandy. The sites are spacious, yet if you pick one in the midde of the grounds you're pretty much out in the open. Each site comes with a picnic bench and a fire pit with a grate. You can buy bundles of wood at the ranger station for 5$ each so make sure you bring cash. The bathroom facilities are clean and there's a decent dishwashing station. There is a lot to do in the area too. I recommend the MA Audubon park, Buzzards Bay Brewing, and Westport Rivers Vineyard.
Month of VisitSeptember