A doctor who treated a woman rescued from the bottom of the country's deepest sinkhole has said she was lucky to survive.
A rescue team brought the 25-year-old Canadian out of Harwoods Hole, Takaka Hill, shortly before 8.30pm yesterday.
This morning she was in a stable condition in Nelson Hospital after suffering shoulder and hand injuries after falling 10m inside the cave.
Dr Michael Brewer told Fairfax she suffered serious rope burns to her hand as she tried to stop her fall.
"It's hard to imagine how you'd survive a 50m fall onto rock if she was going free fall."
The woman's two companions Tuesday night walked out of the Starlight Cave system with the rescue team.
The woman fell while descending into Harwoods Hole, a 176m deep shaft.
The Nelson Marlborough Rescue Helicopter helped extricate the injured caver.
The helicopter crew found the scene using night-vision goggles and then winched the woman on board. She was flown to Nelson Hospital with back, leg and arm injuries.
Emergency teams were alerted to the group's plight just after 12.15pm.
The alarm was raised by a group in the area, police said. The area is remote and has little cellphone reception.
The Nelson Fire Command Unit set up an operation base and a St John helicopter was on standby.
The search and rescue operation was co-ordinated by Tasman Police District.
Harwoods Hole is the country's deepest vertical shaft, dropping to an underground river that flows into the Gorge Creek and the Takaka River.
Inexperienced or poorly prepared groups getting into trouble have sparked rescue operations in the past, the Department of Conservation (DoC) said.
It is not considered a suitable place for learners and DoC describes it as "very dangerous".
Those tackling the hole abseil down the shaft then exit through the cave below.
The trip takes at least nine hours for small groups of experienced, well-equipped cavers who are familiar with the rigging.
Canterbury Caving Group president Yann-Pierre Montelle said he had made the trip through Harwoods Hole three times, and on one of those occasions complications meant he had to re-ascend the hole after reaching the bottom.
"In terms of danger, Harwoods Hole is in and of itself pretty straightforward, but the problem is that people are going in there and they're ill-equipped. Some of them use techniques from rock climbing in a caving environment."
Montelle said the height of the shaft was one of the most challenging factors to him.
"It's pretty impressive when you're on the top of the hole."
In 2008 three people were rescued from the notorious sinkhole after spending hours trapped in the shaft.
Tom Harvey was rescued after seven hours standing on a tiny rock ledge clinging by his fingertips to two small crevices while his fraying rope held him above a 50m chasm.
"It was the single most terrifying moment of my life,'' he said after his rescue.
"It was kind of weird,'' he said. "I was abseiling and it was all really cool, spectacular caves, everything was going smoothly and I looked down and I just saw threads not rope; the sheath had totally gone from the rope.
"I looked up and there was 3m of sheathless rope.''
In 2004 a group of experienced climbers had to be rescued from Harwoods Hole.
The group included a West Coast alpine guide and three DoC staff.