Dion's funeral will be held today at his family farm near Middlemarch, in Otago, and hundreds of classmates, teachers, relatives and friends are expected to attend.
The Weekend Herald has heard from people close to Dion and his friends about events leading to last weekend's tragedy and how the teenager had made the most of a life cut short by a fateful moment.
Dion was raised on farms in Owaka and Middlemarch, where he learned to hunt and fish.
Talented at sport, he was picked to play rugby for Otago at primary school.
Two years ago, he started as a border at Dunedin's John McGlashan College. The boys ate daily meals together, studied together at night and joked together as they went to socials with sister schools - becoming as close as family.
"He came in as a very energetic, promising young sportsman and he was growing up wonderfully. He was pretty much a self-starter," said the manager of the school halls, Murray Munro.
Dion played rugby above his age grade and became known as a tough tackler. "He would take anyone on. He was fearless," Mr Munro said.
The youngster also coached a touch rugby team for intellectually handicapped children.
Six months ago, he joined a running group known for its hard training regime.
Coach Richard Barker said Dion would get knocked around at rugby practice, run 15 minutes to meet the running group, train for as long as two hours, then run back to his hall.
"It's hard [the training]. It hurts. You've got to have the ability to extract the most out of yourself, and Dion could do that," said Mr Barker.
The boy would get up early every Sunday morning to train, and, when he was home on the farm, neighbours in the wider area would see him run past.
Mr Barker said "you wouldn't want to get in a fight to the death" with determined people like Dion - "They never give up."
Dion left school for the Christmas holidays after receiving a merit in graphics at the junior prizegiving.
It had been the last day at the college for his older brother Cody - but nobody realised it would also turn out to be Dion's last.
On New Year's Eve, the day before he died, Dion attended a funeral for his grandfather Syd Latta, who had passed away on Boxing Day.
He then made his way to Wanaka to stay with a close schoolfriend. He had packed his running shoes and went for a long run.
The next day, Dion, his friend and three girls from Dunedin's St Hilda's Collegiate School went to the Motatapu Gorge. The students were escorted by his friend's father.
The gorge is on the western side of Lake Wanaka, a 6km drive up a gravel road and a steep walk down to a narrow river. There are deep swimming holes, and rocks to jump off, and you can make your way upstream to explore a stretch of untouched river closed in by sheer rock cliffs.
It is popular with teenagers, though there have been accidents, including the death of a 17-year-old girl in 2006.
Dion and his friends waded through the river in single file. Though normally one to lead, Dion had let the girls go ahead. He brought up the rear - nobody was as sure-footed as the athletic farm boy.
The group were heading down when Dion disappeared.
His foot had slipped into a narrow crevice, and his torso was over the edge of a 3.5m fall, leaving him hanging upside down.
Water rushed above and below him, pinning him down with such pressure that it is suspected it would have broken or dislocated his limbs.
The teenagers cried out to their friend - and his hands shot out to give them a thumbs-up.
The slip had dropped Dion into an "impossible" position. His head was in an air pocket behind the waterfall, which meant he did not drown and could hear his friends. But the pressure of the water meant he could not get upright to free his foot.
The ensuing rescue lasted more than three hours.
Dion's friends wrapped a net around his free leg and held onto it, fearing he would plunge, while some ran out of the gorge to call for help.
They were only about 15 minutes away from the friend's father, but cellphone reception was patchy.
The teenagers let out cries of frustration as they held on to their friend, but could do nothing to help him.
About 6.30pm, the emergency services received the alarm. Senior Constable Mike Johnston rushed to the scene and made his way up the gorge in a wetsuit.
He told the Herald this week how Dion had squeezed his hand during the rescue even as he grew weaker from the cold, and more than 15 rescuers battled the current to free the 15-year-old.
Eventually, Dion's foot was freed by an elaborate system of ropes and winches which used a rescuer as a dam and made sure the boy would not fall when released.
For the next hour, Dion received CPR in the gorge, within his friends' view from the bridge, while a Dunedin helicopter arrived to lift him out.
Search and rescue spokesman Phil Melchior said Dion had teetered on the edge - the rescuers would think they had lost him but he would come back again.
His friends were "shocked and traumatised" but held on to hope and stayed until Dion was flown away and the scene was cleared.
St Hilda's principal Melissa Bell said the three girls were receiving support to deal with their ordeal.
"It's very difficult for them to come to grips with it. It's a terrible incident."
John McGlashan principal Michael Corkery said: "He was doing what every kid should be doing, playing with his friends in a river."
Everybody had done everything right, but Dion still died.
"It was just a tragedy, and tragedies happen. Life sometimes deals out bad luck but we have to get on with it. We'll never forget him."
