"The way that his leg was pinned - he was never going to come free from that by himself. The power of the water in the gorge is phenomenal."
Mr Johnston said Dion's leg was wrapped around a rock, with water flowing over and underneath. "It was wedged in and there was water pushing down holding it in place."
Before the accident, Dion had been exploring the gorge with friends he had been staying with in Wanaka.
They had been swimming through rock pools and Dion was at the back. When they looked around for him, he was gone.
"They had gone up a bit and were starting to come down," Mr Johnston said. "Where they went to cross, the water was flowing quite quickly and then a narrow chute [opened up] where it went into a waterfall.
"He would have been trying to get to a point where his friends had got to but it's like he's been caught and pushed into the main flow."
One of Dion's friends ran out of the gorge to summon help while the others wrapped a piece of tape around his free leg and held on.
When Mr Johnston arrived, Dion was still conscious and trying to get upright.
Climbers, canyoners and paramedics created a dam to allow a rescuer to get down into the water and put a sling around the trapped leg to free it.
As the ordeal went on, Dion lost consciousness, but he still showed small signs of life. The rescuers did CPR, which continued after he was taken by stretcher out of the gorge and winched up to a rescue helicopter.
"He was conscious for a very long time," Mr Johnston said. "He only became unresponsive at the very end ... He was in shock and extremely cold. I suspect he would have had either dislocated or broken limbs because of the pressure he was under. That will have all contributed to him not surviving."
The rescuers could not hear anything because of the roar of the waterfall but knew Dion was aware they were fighting to save him because he was squeezing their hands."He didn't want to let go of my hand."
Mr Johnston said it was a helpless situation he never wants to find himself in again.
"Every minute felt like an hour ... It was a situation where you couldn't do anything rash or stupid to try to get this young fella out, but not make the situation worse."
He described a complex, mentally challenging situation that required everyone to remain calm and supportive.
"I don't think I've ever been in a more helpless position. It was a struggle between me not doing something stupid and - I think, it was just the separation, of listening to your head and not your heart and letting the adrenalin rush take over. Every minute felt like an hour, waiting for the alpine cliff rescue guys to come and back up the anchor I had put in."
Mr Johnston confirmed amputation was considered to free Dion.
"That was a thought. But I knew if we could get a sling to that leg, we could free him."
Mr Johnston said the area was risky, but popular with young people and adults.
Mike Corkery, head of John McGlashan College in Dunedin, where Dion was a boarder, led the tributes to him last night. "He was a great kid, a good sportsman, just a delight to know.
He was a well-known and well-liked part of the McGlashan family. The whole lot of us will be just mourning him."
Dion's devastated parents, Logan and Sue Latta, of Palmerston, Otago, were being supported by friends and family yesterday.
Other friends posted tributes online. "I know it should have, but it still hasn't hit me that you're gone," wrote Olivia McIntyre. "I go on Facebook and the home page is full with loving posts about you. You will never ever be forgotten, man. Rest easy. x."
THE SCENE
* The Motatapu Gorge is about 15km from Wanaka.
* Dion Latta was trapped about 300m into the gorge.
* The waterfall is 3.5m high.
* Dion was trapped about 0.5m from the top of the waterfall.
- additional reporting: Otago Daily Times
