The Waikato River race strips sport back to something raw, unpolished and deeply human, where participation outweighs performance. Along a demanding 142km stretch of river, competitors are bound together by breakdowns, resilience and a shared journey, rather than the pursuit of status or spectacle.

There is no shortage of iconic boat races in the world. Some are aspirational, others are elitist. The Thames that runs past London hosts both the Henley Royal Regatta and the Oxford and Cambridge Boat Race, which has inspired at least three Hollywood films and many copycat races everywhere from Harvard and Yale in the US, to South African universities racing down the Kowie River in the Eastern Cape.

Other races brave the open seas, traversing the southern Atlantic or circumnavigating the globe. You can sail or row, in a team or all on your own. Unlike the gin and tonics of the regattas or the sweat and blood of the rowing eights, these are more about mental fortitude and grit, and a good dollop of mind-numbing terror, too.

And then there's the Great Waikato River Classic Outboard Regatta in New Zealand, probably quite unlike anything you've ever come across. It's held every Easter and runs for 142km down the Waikato River from the Karapiro Hydro dam near Cambridge, down to the sea at Hoods Landing, Port Waikato.

The river's quite challenging. There are rapids and gorges in places, and in others the water level is shallow, dropping to about...