Room to maneuver: At one point in the tank holds 17 performers

The dancers have not been given any special training or breathing apparatus and stay submerged for up to a minute.

Director-choreographer Sasha Waltz is known for creating dramatic images.

On her last visit to London, with the show Korper (Bodies) at the Barbican in 2003, Waltz squashed her near-naked troupe into a shallow glass showcase.

As its name suggests, Sadler's Wells was built over a well, which was used in the early years to stage aquatic spectacles in a giant tank.

The 1804 season opened with a re-creation of the siege of Gibraltar.

"There were no technical problems involved with the tank," said the theatre spokeswoman. "But there is an awful lot of mopping up after the show."