Civilisation ahoy! A visualisation of the seastead "Oasis of the Sea" by architect Emerson Stepp

"Buy land," Mark Twain famously advised. "They've stopped making it." A century after Twain's death, according to an organisation called the Seasteading Institute (SI), production is resumed.

"Seasteading" is a 30-year-old portmanteau word combining homesteading with the unused resource provided by the oceans: the building of small offshore cities planned outside the jurisdiction of any nation state. The idea originated with Ken Neumeyer in his 1981 book, Sailing the Farm, and SI intends to bring the phrase to life by the end of this decade.

Seastead cities would be built on rigs in areas of ocean unclaimed by sovereign nations. New cities could be linked to existing rigs, creating what the co-founder of SI, Patri Friedman — grandson of economist Milton — describes as "start-up countries".

Building marine cities is not a cheap business proposition, but it is attracting the attention of America's moneyed and philanthropic class. Silicon Valley entrepreneur Peter Thiel, co-founder and recent seller of PayPal, has given almost $1.8 million to the SI. A prototype seastead is pencilled in for 2014, and artists' impressions abound on the web.

Seasteading, however, is as much a political vision as an adventure in construction. The introduction to SI's homepage is barely a few sentences old when it describes existing governments as "like the cellphone carrier industry, with few choices and high customer lock-in". Seasteads are explicitly not just whimsical architectural follies, but "the next generation of governance".