With the world's ice caps melting and global climate change on everyone's lips, it's not such an remote possibility. And with consideration to both super-cities -- New York City counts 9 million people as inhabitants and Tokyo 13 million -- it's not just the shock of major flooding that's worth noticing.
It's how life could change permanently. (In this case, New Yorkers and Tokyoites ought to take a page from Venetians.)
In a series of photos, Studio Lindfors offers a vision in which people, and the cities they live in, have learned to adapt to the overwhelming presence of water.
The message: politics aside, the future of urban planning involves designing with water. Since 70 percent of the Earth is already covered by it, it seems that it's a no-brainer.
Check out the entire photo set for the full experience.