Developers in London claim to be building the world's first sky pool, but an even more extreme suspended glass-bottomed swimming pool is already underway in India (+ movie).

The five-tower Twilight Star development in Surat, Gujarat, will feature a 20-metre-long, seven-metre-wide suspended swimming pool that is entirely transparent. It will link two residential blocks in much the same way as the design revealed earlier this week for London's Nine Elms sky pool.

This pool will be built using similar technology that is employed to construct large aquarium tunnels, though it is not clear what materials will be used.

Despite obvious similarities between the two developments, the Twilight Star swimming pool features a section that projects outward from the buildings – allowing residents to swim beyond the external walls and float over the city.

The Surat pool is also suspended higher up, connecting the 12th storeys of the apartment blocks, as opposed to London's 10th-storey proposal.

Additionally, all of the five towers at Twilight Star will be joined with a glass-bottomed sky walk, allowing residents to move between each of the buildings.

The project is being developed by local company 7 Star and will include 120 residences. The site is located approximately three kilometres from Udhana Railway Station and 18 kilometres from Surat airport.

Construction is already underway and is scheduled for completion in mid-2016, almost a year before London's Nine Elms development is due to be finalised.

Other extreme swimming pools include an infinity pool that covers the entire top of a Greek house, a paddling pool that wraps around the roof of a tower in São Paulo, and cantilevered swimming pools that protrude from a Lima skyscraper like diving boards.