I use the phrase to refer to the waters that link the five terrestrial boros (or boroughs) that comprise New York City as well as immediate adjoining waters. Of course, “adjoining waters” includes all the non-landlocked waters on the planet . . . more than 70% of the “Earth.” I coined this usage of the phrase. Others have used the sixth boro to refer to such things as a retail outlet in New Jersey, parts of coastal NJ directly across from Manhattan, the waterFRONT of various parts of NYC, Governors Island, and others including a figment of the celebrated imagination of Jonathan Safran Foer.
The rationale for my use of the term is that without the watery parts around our fair city, the other five boros would never have evolved as they did. Alternatives to the term “sixth boro” might be the primary boro, original boro, progenitor boro . . . and I could go on. Although there are obvious positioning reasons to name specific parts of these waters, e.g., Buttermilk Channel, Rose Bowl, KVK, Gowanus Bay, etc., it is my hope that the term highlights the oneness of the water around the inhabited areas of the city and accentuates the opportunities that could be harnessed to use the water to alleviate the congestion in the other five boros. Better interface between water and land is my hope.