He won the open and senior titles in the Blaketown Challenge last weekend to become the overall New Zealand bodyboard tour champion with one event still to go. He also won the title two years ago.
The win gives Mackinnon (30), a massage therapy student at the Otago Polytechnic, automatic entry to the Pipeline Pro in February next year.
It is largest event on the world bodyboarding tour and will be held on the north shore of Hawaii.
Mackinnon will start in the fifth round of the main event, allowing him to miss many of the earlier heats and compete against the world's best professional bodyboarders.
"I competed in the event last year but didn't get any good waves," he said.
"I learned a lot and now know how to prepare for it mentally.
"I will be going earlier next year and it will give me time to make use of the experience I had last year."
Mackinnon had never won in Greymouth before.
"I really wanted this win. It meant a lot to me," he said.
"It's just a special event and is a huge part of New Zealand bodyboarding and one my peers really feel matters."
The powerful drifts on the West Coast and flooding rivers made vigorous paddling essential for the surfers. One competitor was sucked out in front of the river mouth and down to another beach across the river 1km away.
Mackinnon hit many large inverts, a move where the wave is used as a ramp to propel the rider up and out in front of the curl.
The rider extends his body and board then brings it back at the last moment before landing. He also executed many back flips out into the wave flats.
Mackinnon posted 19 out of a possible 20, with a perfect 10 for one of his large aerials.
"I injured my neck from a large aerial move the night before the contest and ended up living off painkillers and hot showers to push me through," he said.
He has had a number of injuries since he started surfing 12 years ago, including fractures to his back and neck.
"That is the impact area when you land heavily after doing aerials," Mackinnon said.
In November he will compete with the New Zealand team at the Australian championships on the Gold Coast before he begins his build-up to the Hawaiian event.
