Thinking out loud here, Irene inundated a lot of soundside downstairs units that may not have been "legal."
There are many who add on later, sometimes for storage, or just to cover up the space under the main house. The town code reads something like "Not to be a permanent living area" but for things such as game rooms, laundry, storage, etc.
We built in downstairs on Bay Dr. but didn't put in a kitchen or bathroom. An outdoor shower can be handy April-November. I feel quite sure that unit was flooded from Irene after seeing the pics of the nearby neighborhood.