99% of the living space available on the planet is water, so with a population growth of 1 billion per decade, we need to develop ocean colonization to avoid to cut down the last nature reseve on land to make space for megacities.
Some may argue that there is “still a lot of space left on land”. But the reality is that human pressure on land is already causing the biggest mass extinction of species in history. So to make our presence on the planet feasible we need to reduce human activity on land much below the current (already toxic) level. The only alternative space left that can take this “activity volume” is the ocean.
Read more about sustainability, growth, human population, here: http://concretesubmarine.activeboard.com/t58921987/sustainability-population-growth-consumption-growth-ocean-co/
Even if we could stabilize the “human headcount” on the planet - the activity pressure will still rise as people want, desire, and demand, more and more goods and services to increase their quality of life.
Human settlement of the oceans depends on technical feasible solutions and most of all, a affordable squaremeter real estate price for average joe - this means traditional naval technologies and yacht technologies are very much excluded for bringing settlement on the ocean due to their extreme high cost per squaremeter and dependence on strict shipyard maintenance shedules that a “floating settlement” can not have.
Read more about fesible building methods and squaremeter prices here: http://concretesubmarine.activeboard.com/t57819473/floating-concrete-platforms-building-methods/
Real estate squaremeters floating on the water need to perfom a 200 year service life, and be buildable at building costs compareable to land real estate. Only floating concrete honeycomb and shell structures have this quality.
If you think it trough the most economic way to enclose a living space and make it suitable for human habitation is building a sphere.
There have been recent studies of the MIT for the ORES wind energy storage sistem that place a 30m concrete sphere in a cost universe that would cook down to a real estate price of USD 2122 per squaremeter.
The sistem is planned for 3m thick walls and 400m operation depth. A less extreme sphere with only 1m wall thickness hanging just below the surface would lower this price to about a third of that. This would be already in the range of a normal city apartment.
A sphere habitat would not only be the most economic living space feasible for ocean colonization, it would also be a draupner wave impact free seastead, have low anchor and position keeping requirements, so solve all of the problems seastead engineering is struggling with when designing surface floating platforms.