Perfect conditions awaited the 130 competitors for the 750m swim or 4km kayak, a 20km bike ride and 5km run.
Twenty-eight competitors entered the duathlon section, comprising a 1.5km run, a 20km bike ride and a 5km run.
From the outset, the challenge was between Douglas and Barclay (16), with Douglas eventually finishing in 1hr 2min 36sec and Barclay coming in second overall, and a convincing winner of the junior men's title in 1hr 2min 41sec.
Douglas said he was always aware Barclay - first out of the water after the swim and first home on the bike - would be his chief competition.
"I was chasing him all the way and couldn't run him down on the bike, but finally managed to pass him about half way on the run. Then he sat on me and kept the pressure on, so I knew we would be in for a sprint at the end."
Douglas, an elite triathlete and previous winner of the Lake Hayes Triathlon, said he was still returning to full fitness after a break from the sport while working in Australia.
However, he is focused on competing at the World Triathlon Championships at the Gold Coast in Australia in September.
For Barclay, a member of the Triathlon New Zealand Youth Academy, the race was a test.
"Bobby was always going to be the main opposition and I couldn't quite hang on when he passed me, but I was very happy with the way I raced."
The event was an important build-up for the teenager, who heads to the national secondary schools triathlon at Lake Karapiro later this month.
Second and third went to Wanaka athletes John Metzger (1hr 8min 1sec) and Bruce McLean (1hr 9min 11sec) respectively.
The open women's event was also a tight finish, won by Taryn McLeod, of Dunedin, who defended her December 2008 title.
McLeod crossed the finish line in 1hr 11min 8sec, ahead of Wanaka's Simone Maier (1hr 11min 41sec), with Tamsyn Hayes (Dunedin) third in 1hr 12min 31sec.
"The Lake Hayes course is always deceptively tough, particularly on the bike and the run was hard.
"I knew the others were right there behind me all the way," McLeod saidRace director Tracey Neil said she was delighted with the event.
"There is always such a low-key, holiday atmosphere at Lake Hayes triathlons and that's how we want to keep it.
"But that's not to say the level of competition isn't high.
"After 25 years we are the longest-running triathlon in New Zealand and some of our competitors have been, or have since become, very successful triathletes on the national and international scene.
"It is very exciting in particular to be the training ground for so many junior athletes from around the region."
