The three females and 24 males began the triathlon with a 2km swim in Glendhu Bay, before the gruelling 47km mountain bike from Glendhu Bay to Arrowtown and finishing with a 15km mountain run over the historic Arrowtown Miner's Trail.
Reiser won the event in 4hr 16min 23sec.
He was two minutes behind the leader coming off the bike, but knew he could catch them on the run.
"This is the kind of race we need to put on in New Zealand - it is the real stuff.
"That run is awesome; I think the run is heaps better than the marathon; it's got everything - roads, tracks, downhills, grass and river crossings. Central Otago high country - it can't get any better."
The first female to finish was Simone Maier, of Wanaka, in 4hr 42min 10sec.
Former top ironman triathlete Gavin Hawke, of Christchurch, placed third in the event he dreamed up - dressed only in a pair of speedos.
Hawke finished in 4hr 26min 5sec, behind John Mezger (4hr 25min 40sec).
