Nobbs Radford Architects' proposal was the runner-up in the Architecture Australia Prize for Unbuilt Work, The Sydney Morning Herald reported. They firm came up with the idea after New South Wales Premier Morris Iemma announced in July that restrictions on "secondary dwellings" on suburban lots were being eased.

Alison Nobbs said underground converted pools would allow more housing for Sydney's growing population without dotting the suburbs with large apartment buildings.

"It's just making a suburban experience more accessible," she said. "It's a small, one-bedroom apartment. Rather than being stuck in an apartment building, I guess it allows people access to a suburban experience as well, with a garden and separate dwelling experience."

Manfred Wiesemes, president of the Swimming Pool and Spa Association of New South Wales, believes the plan is unworkable. He said empty pools tend to float when heavy rain saturates the soil around them and the deep and shallow ends of the pool would need an expensive fix.