Image copyright The Seasteading Institute Image caption A mock-up of what one of the floating platforms might look like incorporates local design elements

French Polynesia has signed an agreement that supporters hope could pave the way for autonomous floating cities around the world.

The tiny Pacific state signed a memorandum of understanding with California's Seasteading Institute in San Francisco on Friday.

It outlined objectives the institute must meet to get possible go-ahead for its first "seastead" community, off the island of Tahiti.

But the floating futurists themselves admit it will be anything but plain sailing to realise their dream of sea-borne social experiments floating around the world.

What is being proposed?

"I don't think it will be terribly radical at first," the institute's executive director Randolph Hencken, told the BBC.

Image copyright @Seasteading Image caption Jean-Christophe Bouissou, French Polynesia's ministerial representative (centre) was pictured with Seasteading's Randolph Hencken (right) and Joe Quirk (left)

For a start, it will be in French Polynesian territory, close to shore and protected from the high seas.

Seastead plans often involve them being in international waters to create a libertarian utopia free of landlubbers' laws.

This agreement leaves open the question of what freedoms the floating community will be granted by the government.

Mr Hencken is confident that having invited them to make their proposal, the authorities will grant them "leeway" to govern themselves and their "special economic sea zone".

What are the hurdles?

The deal specifies two points the project has to prove - whether it will benefit the local economy and whether it can avoid damaging the environment.

Only then will work begin on developing what the institute calls a "unique governing framework", and even that will need to be approved by the local government, and potentially France, which ultimately holds the territory.

Image copyright Andras Gyorfi Image caption The institute has previously held design contests, although this past winner is not the proposed design for the French Polynesia project

"I'm confident it'll happen but there are a lot of moving parts," Mr Hencken admits.

Not least of which is considerable uncertainty over what the sea-going village - visions of a marine metropolis are still floating over the horizon - will look like, architecturally or socially.

The former is little more than computer generated images so far, and as for public services and paying for them, Mr Hencken admits it is a blank slate.

"A lot of these things, while they've been discussed over camp fires, haven't yet been selected," he says. "Our ultimate goal is to create space for any experiments... not exclusively libertarianism."

Sustainable seafaring?

The institute says its communities will be sustainable, shunning fossil fuels and destructive use of the seas.

But with many prominent seasteading supporters famously keen on eliminating taxes and regulations, critics are unconvinced sustainability is the real goal.

The institute itself was co-founded by Silicon Valley's best-known Donald Trump supporter, Peter Thiel, and several of his associates are among its staff.

Image copyright AFP Image caption Supporters claim floating communities could help low-lying countries survive sea level rise

Mr Hencken insists living closer to the sea will reverse the attitude that "oceans are a hunting ground, a superhighway and a garbage can."

A leg up from the landlubbers

Whatever the motivation, it is a dream that is not short of ambition - floating social Petri dishes where each can experiment with new ways of living - but it is ironic that the first practical steps towards achieving it are in territory owned by one of Europe's most interventionist states, France.

Mr Hencken praises the stable institutions, friendliness and security of the "paradise" of Tahiti, in contrast to some more freewheeling and corrupt places they have considered in the past.

If it fails, it will join a long list of doomed futurist daydreams, but if the "pilot project of just two or three platforms" grows into a global social experiment, it may ironically have landlubbers to thank for helping set them out to sea.