Sorry, but “Venice” usually refers to the city, not its various possessions, which at different times have been scattered over much of the eastern Med coastlines and islands and northern Italy.
But in Venice, circa 1600, the areas on the mainland around the lagoon were considered part of Venice in much the same way that the west end or east end or southside are considered part of London even if they are well outside of "The City", or original walled area founded by the Romans.
Not today, of course, since for the most part they are no longer there. Venice has been a shrinking city since about 1750, probably earlier. And it had more to do with economics (the decline of the Venetian Empire as a trade center) than it had to do with industrialization, rising sea levels and the like.
Still don't believe it? Look at exactly the reverse situation in the Netherlands/Belgium. Before 1600, they were colonies of Spain and economic backwaters. Once they became economic trade centers, they reclaimed land from the sea exactly as Venice had done during its peak, albeit with more modern technology.