Some development and research has gone into the concept of having underwater living complexes. During the 1960s through to the mid-1980s the USA began investigating this possibility through its underwater habitation program. Headed by the US Navy several divers lived in underwater buildings in the shallows at depths of around 10m. They proved that it could be done and the divers themselves lived under water for weeks at a time. So why hasn't the concept gone further? Some futurists and experts argue a compelling case for taking the concept further.
On paper having cities underwater would certainly go a long way into dealing with the over-population concerns now taking shape across the world. Many in the space agencies and the corridors of power look to the stars to seek answers from soaring numbers in cities and towns, but some reason that it is the below the surface the answer truly lies. Over 70% of the world is covered by water so making use of it would certainly make sense in proportion to the land mass available. Indeed many sections of continental shelves close to land would prove ideal sites. At depths of 100m or more from the surface a good sized city anchored into the earths crust would give excellent protection from hurricanes, storms and even meteorites! With water processing plants providing clean water for the inhabitants and power coming from relays of tidal wave collectors or building a city near geothermic vents the city would be to a certain extent self-sufficient from the outside world.
Even though we are in the dawn of the 21st Century, cities underwater still has the ring of science-fiction to it. From the practical aspect the massive amounts of spending required to build and maintain an underwater complex would mean that it would undoubtedly require a massive joint effort from several countries. Unless there is a breakthrough in hydroponics most of the food supplies would have to be imported via supply subs as the lack of sunlight would result in little or no photosynthesis to grow foodstuffs. Living underwater is essentially akin to living under a hostile environment, an accident, rogue action or sabotage could easily lead to catastrophe amongst inhabitants.
Another avenue for the underwater population concept is in the industrial sector. Fossil Fuels aside, valuable resources such as diamonds and rare minerals are known to exist underwater. If an area were to be found where they were concentrated in abundance it would prove a strong case for development of underwater mining operations. The cost in running such an operation would likely be exceeded by the bounty reaped from the depths. Already above the ocean surface offshore platforms bustle with activity extracting precious hydrocarbons (oil, gas etc), why then should an underwater version be overlooked?
Underwater Cities In Popular Culture
'Bioshock.' A popular game released on the Xbox 360 in 2007 was set in a fictional underwater city called 'Rapture.' It was located in the middle of the Atlantic Ocean and was powered by Geothermic vents. Although the game is far-fetched and more horror orientated than realistically feasible it shows that the idea and imagination for underwater cities lives on...
Currently there are some small shallow water self-contained habitats in operation but these are mostly for scientific and research use. Only time will tell if they will mark the extent of mankind's progression into the depths...