But the young Dutchman, who stems from boat building and architecture stock, dove right into his new job, and it wasn't long before he started making connections between the principles of a floating house, and the battle the Dutch have been waging against the sea to reclaim land and stay dry for 500 years.

He thought, if a house can float, why not an office complex or a structure big enough to hold a whole city?

Olthuis, who along with building partner Dutch Docklands, designed a section of floating islands for Dubai's man-made Palm Islands development project, has also created a patent which scales up the technology used for a houseboat to floating structures big enough to hold cars, roads and houses.

"Water is a workable building layer or a floating foundation and if you turn water into space, which is a dramatic change of mindset, there's a whole new world of possibilities," Olthuis told Reuters.

He said the basis for his design isn't any different than the normal Dutch floating technology used for houseboats.

"It is just a floating foundation, mostly made of concrete and foam which is quite stable, heavy, and goes up and down with waves and up and down with the sea level," he said.

The floating city of the future is still a dream, but Olthuis's firm, WaterStudio, which he started a decade ago, designs buildings and floating structures which try to combat the challenges posed by rising sea levels.

"Because of urbanisation and climate change, all the big cities have space limitations. We can create space with water, space that others have never even seen," he said.

He said he wants to create space where land is under threat from rising sea levels and compares the methods for building floating structures to the invention of the elevator.

"If the elevator were never invented, then cities wouldn't have buildings with more than three or four levels, because nobody wants to walk up more than that. But with elevators, we can climb 20, 30 even 40 flights."

Olthuis's firm has designed plenty of floating homes in The Netherlands and is laying plans to start building an entirely new floating neighbourhood with 1,200 homes.

It has projects in India and China and has begun preparing the lagoons for a holiday resort project in the Maldives, a chain of islands in the Indian Ocean that is one of the world's most endangered nations due to flooding from climate change.

"We started thinking seriously about designing a whole floating island when we got a request from the Maldives, which are threatened in the long-term by rising sea levels, and they are looking for new development opportunities."

In response, Olthuis's team and building partner Dutch Docklands designed an estate of 185 luxury floating villas, called The Ocean Flower, part of a larger development across five lagoons, including a conference centre and a golf course.

The islands are designed to move with the waves and sea levels but because they are so stable, Olthuis said being on one of his artificial islands is like being on normal land.

"You do not feel any waves."

The islands will be connected to the seabed with the same sort of cables used in offshore technology, for oil rigs, which lets them stay in one location and not drift away.

"The development in the Maldives is for a happy few who can afford to buy their own floating holiday home," Olthuis said.

But he said that building luxury resorts for the rich helps to refine a technology that can in turn be used to benefit the poor in places such as Bangladesh, where flooding regularly destroys lives and livelihoods.

"So we let the rich pay for the innovation for the poor," he said.

Olthuis said future designs could see floating structures detached and moved to new locations, or new cities, put together like a puzzle, responding to particular urban needs.

For a man who was told as a young trainee to "forget about houseboats," Olthius's focus on water has had a resounding impact on the way he looks at space and the environment.

"I am a Dutchman, and for me, Holland is an artificial country. It is all fake. We live below sea level and it takes too much effort and money to keep the pumps working 24 hours a day," he said.

Olthuis said that within 50 years, it won't even be possible to pump all the water back to the sea and reckons it is time for the Dutch to forge a new relationship with water.

"We need to learn to live with it rather than fight it. We should let the water come back, and then build on it." (Reporting by Roberta B. Cowan, editing by Paul Casciato)

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