Park near Salem, MA?

We stayed at Winter Island in July, actually over the July 4th weekend. There were 2 areas for your RV one was in a parking lot down near the water and you can have a site on the water and the site we had was in a field. The sites were small but it was okay for the time we spent in the park and our neighbors were close but wonderful people. We caught the train in Salem and rode it to Boston for the day for $21 an adult roundtrip and the kids were $14 roundtrip. Winter Island had a lighthouse, public beach and an old fort. I was concerned about the bathhouse being shared with the beach people but never had to wait for a shower and they were always clean. We could have dumped at the sewage plant when we left but we wanted to be on the road earlier than the time it opened. If we have the opportunity to return we will not hesitate to stay there again. We paid $37 a night for our site and I think the sites on the water were a few dollars more.