Kate Bush spent three days submerged in water in a flotation tank to create special effects for her live shows.

The 55-year-old singer, who will take to the stage for 22 concerts at the Eventim Apollo in Hammersmith, London later this year, has hired a movie tank at Pinewood Studios, where she has been practicing a 'lost at sea' scene in which she is rescued by a helicopter.

A source told the Daily Mirror newspaper: ''During her concerts there will be lots of footage and special effects.

''Kate wants the show to be out of this world and hired the underwater stage which is fitted with a wave machine and special lighting at Pinewood Studios.

''She spent three days in the tank re-shooting scenes and performing her songs. She wanted to create the effect of her floating in the ocean, lost at sea.

''The footage ends with her singing 'Hello Earth' and being saved by a helicopter.

''Special technicians re-created the helicopter by using ceiling fans.''

The recording was given the code name 'Navy Blue' and the pop star performed hit songs including 'And Dream of Sheep' and 'Wake Up'.

Despite being underwater, the crew working on the scene were reportedly ''gobsmacked'' by how powerful Kate's voice was.

One staff member said: ''We were all brought to a complete standstill as she sang, her voice is absolutely incredible, it was completely flawless. It was the most beautiful thing some of us had ever heard.

''She may have aged but her voice hasn't changed.''

Kate has reportedly ''thrown everything'' into the highly-anticipated live shows and millions of pounds are being spent on special effects, costumes and staging.

The gigs, which sold out in just 15 minutes, are kicking off on August 26, with seven new dates at the end of September and in October added just last night due to massive pre-sale demand.

Kate's announcement comes after her 'The Tour of Life' shows in 1979, which had until now been the only concert tour of her career.

The six-week tour took her around Britain and mainland Europe and ended at the Hammersmith Odeon - now called the Hammersmith or Eventim Apollo - the venue she has chosen to return to.