But even with the odd crash, the 18-year-old is still hoping for a top-15 finish at the triathlon age-group world championships in Switzerland later this month.
The year 13 Otago Boys' High School pupil has been selected in the New Zealand under-19 team.
He will contest the sprint triathlon, which consists of a 750m swim, 20km cycle leg and a 5km run.
He leaves for Christchurch today and will fly to the United Kingdom to visit family and complete his preparation, which includes a race in Slovakia.
He will be away for the best part of a month. It is quite a trip and Jack also plans on visiting Loughborough University while over there.
He hopes to attend the institute.
He is a studious young man, well, mostly.
"We'll see," he replied when asked if he would be lugging some textbooks along with him.
Jack started off as a swimmer but got to the point where he was "a bit sick and tired of it".
"It got pretty repetitive so I wanted to try something new. And I've always done a bit of running and cycling and just thought I'd put it all together."
His uncle, Michael Lawrence, was instrumental in his move to triathlon.
"He was sort of like my first coach in a way. He wrote me some session plans and I went out for a couple of trainings."
That was just two years ago, so Jack has progressed quickly.
It will not be his first time at the age -roup world championships.
He was selected for the New Zealand team last year and finished 17th in his category on the Gold Coast.
But he has had a few setbacks in training recently.
He broke his collarbone at the start of May after tumbling off his bike.
"That put me out of training for eight weeks and then I had another bike crash in the last school holidays. My legs got infected from the road rash and I missed more training.
"So I haven't really had a good run with training because I've been trying to do rehab."
Jack has had to lower his expectations as a consequence.
"I can't be too hard on myself because I know I won't be able to race to my full potential."
That said, he is still hoping to improve on his result last year.
"I got 17th last year so I think it [top 15] is achievable."
Jack is coached by former Olympian Tony Dodds who started competing in triathlon when he was 17. He was a late bloomer like Jack and an inspiration for the young man.
He hopes to follow Dodds' path and compete at the Olympics and Commonwealth Games in the future.
More immediately, he hopes to gain selection in the junior elite team next year.
