Shimizu Corp is a company that is planning for the future and it is looking to the ocean floor. They are visualising people living in an eco-friendly undersea city within 15 yrs while capitalising on the 'infinite possibilities of the deep sea'.
The city would consist of a floating sphere (500 metres in diameter) just under the surface, housing business and residential zones and hotels. The structure would connected to the seabed 3-4km below by a spiral pathway. Energy resources at the seabed will bring the three section of the city to life using ocean thermal energy conversion .
More information at these websites
http://www.shimz.co.jp/theme/dream/oceanspiral.html for further artist rendering