"I lost 30kg five years ago over a 12-month period through calorie restriction and exercise," he said.
"I started walking then slowly adding running until I was able to run for 30 minutes nonstop. Then I focused on doing a half-marathon, then a full marathon, then it was 'what's next?'."
Next was the Heaphy Five-0, an 80km trail run on the Heaphy Track, located just 25km from his Golden Bay home. "Then I felt I needed more balance in my exercise so I got into road cycling, doing events like the Source to Sea and Grape Ride and the Lake Taupo Challenge. To keep motivated with my exercise I like to have a goal ahead of me, so again, it was 'what's next?'."
That's when the Coast to Coast first came into Garrett's view.
With no kayaking experience he enrolled in a four-day white water course to get started and then completed additional courses with Sam Milne from Canterbury Kayaking and some guided trips through the Waimakariri Gorge.
"Last year, I weighed 98kg and did the individual two-day event. I had a fall in the run that added an hour to my time, and during the kayak I had all these faster kayaks passing me so I was busy on the river planning 2015 to come back stronger and faster."
Despite his worries over potential weight gain, Garrett, with the aid of leading nutritionist Ben Warren, managed to emerge lighter at the end of his nine-week convalescence.
"With Ben's BePure programme of eating to my body type I have dropped from 22 per cent body fat last year to 15 per cent this year and gained muscle strength that will be beneficial in an event like the Coast to Coast."
He is now single-minded in his focus, just four days out from the event.
"I'm really looking forward to making it to New Brighton this year. All going well, 2016 will see me take on the longest day."