The sky's the limit for the latest jaw-dropping swimming pools. Clinging daringly onto the side of tower blocks, perching dizzily atop high-rise balconies or cantilevering vertiginously off rooftops they all cost big bucks and many include wow-factor features such as transparent sides and bottoms.
It's a far cry from the familiar rectangular patch of blue located at back of the suburban backyard or apartment block.
One of the most 'out-there' projects is the proposed 30 storey Parinee ISM, designed by Hong Kong-based James Law Cybertecture for Mumbai. Construction will start in two months with completion expected within three years.
Law's photo-realistic images depict a series of 64 fantastical, infinity edge pools – each 1.5m wide x 8m long x 1m deep – situated on balconies that rise up a futuristic 140m tall residential tower.
"Inspiration for the pools was the ripple effect generated by water droplets," Law said.
As his rendering depicts pools that extend right to the balcony edge, it isn't hard to imagine swimmers floating right over. "The depth of water, thickness and height of the glass provides safety similar to a typical balcony," Law said.
Andrew Nimmo, Adjunct Professor of Architecture at the University of Sydney, is left wondering. He acknowledges that pools such as these are do-able in theory, albeit with the input of a structural engineer and at an exorbitant cost.
"But the glass edge appears to cantilever out from the deck and it would have to withstand the dead load of the water plus the live load of someone swimming and bumping up to it," he said.
Structural engineer Mike Murphy of M J Murphy said that a better alternative to glass would be acrylic - and in a thickness of 80 mm to 100mm.
"Acrylic can be designed to withstand impact loads whereas an engineer can only design glass panels to lower the breakage possibility, not eliminate it altogether. If glass fails, it fails instantly and catastrophically," he said.
According to Nimmo, it will also be tricky to maintain the safety barrier between the inside living areas and the outside deck. "Effectively the glazed doorway will have to perform the role of a pool fence, with self-closing doors and latches above 1500mm to prevent an unaccompanied child gaining access to the area. It is a safety nightmare."
Surprisingly, though, Nimmo said that the weight of each pool was not so much an issue.
"It's feasible to design the concrete to hold the enormous weight but the drawing shows no indication of any columns and only a fairly thin concrete edge, so there is much license in this [early] image.
"The practicality of trying to contain the water from cascading down the building caused by high winds and people splashing makes this, in my opinion, a silly idea."
Murphy agreed there could be problems unless a retaining balustrade was extended up to a safe level above the water.
"Alternatively, water overflow will need to be controlled by having a lower trough to stop it travelling to the balcony below," he said, adding that "wild architectural dreams must always be brought back down to earth by engineers' practicalities".
One breath-taking infinity edge pool with a wide catchment this is already in existence is located atop the 55 storey Marina Bay Sands hotel in Singapore. The recently-completed, 150m pool is sited on a platform that overhangs the building's northern tower by 67 metres. Disconcertingly, it looks across the top of the city's skyscrapers.
"Only in a Dr Seuss book did I think it was possible to swim amongst the clouds," said Nicole Lenord, who took a dip there with her family when visiting from Sydney recently. "But after we had overcome our feelings of vertigo, we relaxed and swam with the birds!"
Another sky-high, look-at-me pool is located on the 24th floor of Holiday Inn's Shanghai Pudong Kangqiao. The deep end of this 30m pool projects out from the building and there's nothing but a toughened glass base between it and the pedestrians way down below.
Away from the urban jungle and in an actual jungle, one real cliffhanger pool can be found at Bali's Ubud Hanging Gardens resort. Two-level, curvaceous and with infinity edges, it overlooks a deep ravine of green.
So, is anything similar making a splash on home turf? An early adopter in 1992, was Melbourne's Adelphi hotel with its 400mm thick, laminated glass-bottom lap pool jutting out nine storeys above Flinders Lane, but it's in Queensland where some of the most breathtaking pools can be found.
Brisbane-based business Aquatonic have designed and built several spectacular pools which appear like giant-size ice blocks giving the illusion that the water is without any visible means of containment.
For a 27th floor penthouse pool on the Gold Coast, three huge panels of Plexiglas (each weighing around 1.1 metric tonnes) have been craned into place; and a similar acrylic-sided infinity pool graces the roof terrace of a new three-storey Sunshine Coast house.
Aquatonic's MD, architect Marco Giaroli, said that building on balconies like the Indian project would be tricky in Australia due to the pool fencing code. "Lack of privacy could be an issue, too. But, with enough money, anything is possible."
He suggests that a more bang-for-your-buck use of acrylic would be to include a pool window that looks into the home's living room aquarium-style.
In a similar vein, Murphy's NZ-based company has recently undertaken several projects at Conrad Maldives Rangali Island. Two pools on piers extending out over a sheltered lagoon were built for each of two luxury villas-on–stilts.
But even more eye-wateringly amazing is the resort's underwater restaurant contained in a transparent tunnel. You don't swim, but the fish around you do. At four metres below sea level it's not exactly terra firma, yet it's arguably more down-to-earth than the balcony pools proposed for India.