Jeffrey Linn of the blog Spatialities has mapped what New York City would look like under an additional 100 feet of ocean. The Jersey side has turned into an island, while only small parts of Manhattan, Brooklyn, Queens and the Bronx remain above water.
The map draws on a U.S. Geological Survey data that estimates that complete melting of the current global land ice mass could raise sea level by up to 80 meters, about 262 feet. This won’t happen overnight: In fact some scientists believe this kind of melting could take 1,000 to 10,000 years. Still, some day in the future Brooklyn Heights could become the Brooklyn Depths.

New York under 100 feet of water (larger)