Glowing Sea, it seems to me that strongly suggests that the area is in fact a large body of water. Cant believe people want to suggest otherwise, what is it really a Glowing Marshland? If it turned out too be a Marsh or other traversable by foot terrain feature that is submerged by water then technically the area its in is still in Boston, a place that experiences freezing temperatures for a good part of the year. So if its a marsh what is it renamed the Glowing Tundra during Winter?
For that matter it'd be odd for a marsh, bog, or what have you to be up around Boston area but oh well.
Its likely the Harbor was just renamed or the Ocean.
200 years, I can see all sorts of area's being renamed by whats left of humanity.
PS
Forgot there is also swamp, an area of land submerged under water, can be quite deep, and in fact what is there could all just wash out if it wasn't for plants being there to hold in the sand, mud, or muck.
I just don't see how that would work.