Milne has been involved in adventure sports since he was a teenager.
He rowed from the age of 12 to 21, including representing New Zealand. His highest achievement was a gold and two bronzes at the 2007 Youth Olympics.
He also represented New Zealand in duathlon at the last world championships. His best result was a bronze at the 2011 world long-distance champs followed by a silver at the world standard distance champs two weeks later.
Milne loves the competition at the top end of the Brass Monkey.
"The competition is always really tough at the Brass Monkey. Not only are most people out to win, they're out to beat their mates, training partners and themselves. It makes for a good battle."
Milne fits in one to two hours of training each day on the water and also juggles the training for multisport and adventure races.
His next mission is a five-day adventure race in Mongolia at the end of August.
But first up, bragging rights in the Brass Monkey are the priority.
"It is tough to get out in the cold and more times than none your hands are numb and you can't feel your paddle but once you're moving and warm up it's all worth it. You've just got to remember the person next to you is just as cold.
"I find paddling the Waimakariri River peaceful and a distraction from the [earthquake] devastation around us here in Christchurch."
While Milne prides himself on setting the pace in the event, he stressed that any level of athlete would handle the challenge of the Brass Monkey.
"Anyone who is up for a challenge can do this," he said.
"River paddling isn't just about strength and fitness, you've got to be able to read a braided river, too, which adds another element to this sport. Someone that's not as strong but has really good river reading skills has a good chance at winning. Being able to to stay upright in a kayak is a big bonus, too."
For many the most important part is afterwards.
"Everyone hangs around for a beer and prizegiving. This is usually when the banter starts. With the energy we have left we never fail to have a good laugh. Whether someone ran aground, went the wrong way or threw up all over themselves - everyone seems to get a bit of stick for something."