All aboard: Are these the cities of the future?

There could be an innovative solution to the problem of congestion and overcrowding in Aussie cities - but it might be a long way off.

A California-based non-profit, The Seasteading Institute, is floating the idea of "Seasteads" - ocean-borne cities that will give people opportunities to peacefully test new ideas about living together.

Creators say it could be the way forward particularly for Pacific nations forced to deal with rising sea levels.

But to ease the big squeeze in Australian cities, these man-made ocean suburbs would need to house tens of thousands of people.

Monash Infrastructure director Professor Graham Currie said the world was under pressure with land.

"From an engineering perspective, you can get it to happen," he said.

And Sydney University civil engineering guru Hillary Pan agrees.

"It is do-able. The design is sound," she said.

Ms Pan has proposed the floating structures be built about seven kilometres offshore - far enough out to use the sustainable energy sources of wind and wave action, but close enough for a reasonable commute to the mainland.

"I thinkt he benefits would be decreasing the density within the mainland city itself, and also giving people a chance to move onto the ocean, where you can argue the air is fresher," she said.

However, Prof Currie said there would be worries about changes in water level and even waves.

He said not expect a sea change any time soon.

"You'd need to have a lot of really good reasons to do that and I think we're quite a long way off needing that type of infrastructure," he said.