A US organisation is hoping a plan to create cities which float on the ocean will see them not only produce their own food but establish their own governments.

The Seasteading Institute says it hopes the floating microcountries will allow for experimentation with new ideas which current governments are too large to try.

Seasteading communication director Joe Quirk says the floating cities create room for "start-up governments".

Sorry, this audio has expired Floating cities: the way of the Pacific future?

"When you consider that nearly half the world's surface is a blank slate, unclaimed by existing governments, you see the potential in creating a thousand start-up governments in the sea," he said.

"Seasteading comes from a very Silicon Valley perspective, that basically we don't think 193 national governments represent the range of ideas that 7 billion creative people have produced.

"We think we need a sort of start-up sector for the government, a sort of Silicon Valley of the sea, where 21st century ideas for governance can be tried.

"We're creating, literally, a platform for anyone to try whatever kind of nation they want."

The Seasteading Institute says the first prototype city, made up of modular square or pentagon shaped platforms, could be built by 2020 and house about 225 people.

Mr Quirk says they are looking for a nation to host the city in its shallow territorial waters and provide it with substantial political autonomy.

"We hope that if we can set an example, provide some jobs and create some eco-cities that float in the shallow territorial waters, we'll set an example and show people that seasteads can be of benefit to the world," he said.

Mr Quirk says the engineering technology for smaller seasteads already exists.

Shell's Prelude FLNG platform has decks 488 metres long and 74 metres wide, and is designed to remain at sea for 25 years ( Shell )

He says structures like Shell's floating LNG platform Prelude, which is bigger than the Empire State Building and designed to remain at sea off Australia's west coast for 25 years, are paving the way.

"If you think about cruise ships, cruise ships are the size of skyscrapers and people attend rock concerts in them," he said.

"Just about anything that you do on land, people do on cruise ships.

"So the cruise ship industry has largely commandeered this space, it's just about getting permanent structures out on the waters that hopefully would be politically independent."

It is also hoped the technology could offer a solution for the Pacific Island nations under threat from climate change.

"The world is full of people who need to leave their countries and island nations because of rising sea levels," Mr Quirk said.

"We want to get a good example as quickly as possible, show that the technology is possible and hopefully attract more investors in the future to possible rescue some of these nations."