A picture of a seemingly gravity-defying pool perched on the 55th floor of a London sky scraper has been circulating, and terrifying, ground-dwelling humans this week.

The 600,000-litre pool is the brainchild of Compass Pools – an innovative pool company that is hoping to make this invention a reality in 2020.

The unusual construction would be made from an acrylic material, rather than glass, to give the pool the appearance of being crystal clear. In other words, the pool will look as though its a cube of water hovering over the building.

Alarmingly, for those who don’t love heights, the floor of the pool is also transparent, so swimmers can see below – and visitors within the building can look up to see swimmers in the sky above.

But how on earth do you get in and out of this thing? Apparently, swimmers will access the pool through a rotating spiral staircase that is based on the door of a submarine, that rises from the pool floor when some one wants to enter or leave.

And, ground-breaking wind-reading technology will ensure water doesn’t get blown out onto the streets below. The pool’s heating system (it is London, after all) will use waste energy from the building’s air conditioning system.