The Carolina Bays and the similar formations elsewhere in North America began simultaneously as ejecta craters from an event located in the midwest.
I liked the note that pointed to their having an origin somewhere about SE Indiana and SW Ohio.
I have hope for the volcano South of Seymour, Indiana having had intermittent activity within the last 100,000 years ~ that'd explain all your "bays".
That would also make them land features and not bays at all since sea level would have been lower than the bottoms of those bays through that period.
There's another lurking cauldera in the vicinity of Paoli, Indiana and up to Martinsville, Indiana.
These things are supposed to be OLD and inactive, but there's a heat source still cooking water for them.