Why do most other local divers not work through the winter? You don't haul for the winter in that area, do you?
The Chesapeake gets a lot of cold water runoff from the mountains of WV, PA and NY. The further north you go up the Bay the more brackish the water becomes and also colder. Potentially, it will get colder and freeze over sooner than that other nearby coastal bodies of water like Long Island Sound that are influenced by the Atlantic. In '77 the Bay froze over completely land locking Baltimore for a brief period of time.
Many people haul their boats so they don't have to deal with ice, bubblers or frozen bilge pumps.