Memorial Park in Mosgiel was transformed into a mass of youthful energy as parents and supporters cheered the 828 children taking part in the Dunedin leg of the national series.
• Slideshow: Kids Tryathlon
Moments after becoming the first 9-year-old to complete the swim of 75m, 4km bike ride and 1.5km run, Theo Smith said, ''It was fun ... and pretty easy.''
The Kaikorai Primary pupil, who enjoys gymnastics and diving, said the hardest part was getting ''a really bad stitch'' during his sprint towards the finishing line.
He was presented with a medal by former basketball star Dillon Boucher, one of several identities, including cyclist Alison Shanks, presenting medals.
A spokesman said more than 1000 7 to 15-year olds took part in 2013, so numbers were down, but the feedback indicated this year's event was extremely popular.
''The children were very enthusiastic.''
The Dunedin leg - the eighth of 14 Weet-Bix Kids Tryathlon events around the country - attracted participants from Otago and Southland.
Feedback indicated some parents wanted an event in Central Otago and ''we are always looking at areas that we could expand into,'' the spokesman said.
It was the 15th year Ian Paulin, of Dunedin, had been assisting.
He helped enlist the 100 volunteers providing marshalling services for participants and spectators.
