The extraordinary three-hour rescue of the 15-year-old is detailed in LandSAR Wanaka volunteer Phil Melchior's book, Mountain Rescue - epic tales of search and rescue in high-country New Zealand.
Dion's foot was caught and he was dangling backwards over a waterfall.
His head was in an air pocket between the rock face and the rushing water, enabling him to breathe, but the immense pressure of the water meant he could not get himself upright.
Massive efforts to free him succeeded only when LandSAR volunteer Milo Gilmour created a human dam to reduce the water pressure, enabling Mike Johnston, a police search and rescue team member and LandSAR volunteer, to dive underwater and release Dion's foot.
But Dion died next day of hypothermia caused by hours in the freezing water.
''It was such a humongous struggle for everybody involved,'' Mr Melchior said.
''An extraordinary struggle by him to survive as long as he did. The process of freeing him was a monstrous task.
''We were very proud of the fact he was still alive when we handed him over. Keeping him alive was a huge effort. To have it all go wrong the next day ... really knocked everybody around.
''Everybody who was involved went over and over 'what could we have done differently, what could we have done better, could we have got him out sooner than we did?' Realistically, the answer was no to all of those things.''
Seasoned coroner David Crerar described evidence at the inquest as ''the most harrowing'' he had read; three of the rescuers received bravery awards, and the entrance of the new gymnasium at Dunedin's John McGlashan College, which Dion attended, was named the Dion Latta Foyer, in his memory.
- Jessica Maddock
