David Blaine was unconscious and having convulsions when he was rescued from his water tank during a breath-holding stunt, his trainer has said.
"If we hadn't intervened, he would still be at the bottom of the sphere doing a breath-hold," said Kirk Krack.
The US showman held his breath for seven minutes, two minutes short of the world record, when he started struggling and was pulled out.
The record attempt followed seven days in a human fish bowl in New York.
"I wasn't focused on records, I was thinking of a rescue," Mr Krack, a free-diving expert, said.
Blaine was "unconscious when we brought him to the surface", Mr Krack added.
Blaine managed to hold his breath underwater for seven minutes
The illusionist left hospital on Tuesday, one day after the dramatic televised end to his latest stunt.
"He still feels today that he let people down," his doctor Murat Gunel said.
Blaine's liver and kidney functions and skin had suffered while he was submerged but are now improving, he said.
Dr Murat Gunel said there was evidence of liver failure on the second day. "I told him he needed to get out of the water, and he refused," he said.
"He said he did not want to let the people down."
But Blaine wants to try the breath-holding record attempt again, he said - but without spending a week under water first.
Before embarking on the stunt, the 33-year-old US showman shed 50lbs (23kg) in body weight to improve the efficiency of the way his body uses oxygen.
But Dr Gunel said the strenuous training and weight loss made Blaine too tired before he entered the sphere.
Crowds of spectators and millions of TV viewers saw him rescued.
Blaine was well enough to thank supporters before leaving for hospital.
"This was a very difficult week but you all made it fly by with your strong spirit, your energy. Thank you so much everybody," he told a cheering crowd in Lincoln Square.
Blaine's previous stunts have included spending 61 hours inside a block of ice and fasting for 44 days in a Perspex box over London's River Thames.