When I was a kid there was a lot of hype about human habitats on and under the sea. The sea was touted as the next frontier (space having already been conquered, symbolically at least, by the Apollo missions.) Decades later– off-shore drilling platforms notwithstanding–the oceans are still mostly a mystery and cities in the sea are still just futurists’ dreams. One of those futurists, Jacque Fresco, dreams in 3D at The Venus Project. There are some cool ideas and images related to future visions of construction and transportation systems, as well.
As for me, I gave up wanting to live under the sea after seeing Jaws.