Although team cyclists Tom Francis, a former New Zealand triathlete, and ironman competitor Paul Baskett went ahead of Page in their duathlon event, the policeman maintained his lead in the individual multisport race.
"Jason's plan by the looks of things was to go hard in the run and the cycle and try build up a big enough of a lead going into the kayak over Aaron in the hope of holding him off in his favoured leg," said Holmes.
"The plan was on track for the first two disciplines, however Aaron was too strong in the kayak, overtaking Jason during the first of two laps on the river between the Dublin and Railway bridges."
The previous days of rain had raised the river level, making it quicker to paddle down but more challenging than usual coming back.
Cox finished in 1h 23m 26s with Page coming in just under four minutes later, while Matt Foster was third.
The women's race was won by Sapere Simon in 1h 45m 26s, just seven seconds ahead of Kylie Gibson in a tight finish.
In the Short Course Duathlon - 2.5km run, 10km cycle, 1.25km run - Briley Zimmerman was the first home in 36m 39s, continuing her buildup for the World Duathlon Championships in Adelaide this October.
Te Mana Kaua was second overall and the first male, finishing in 37m 41s.
There were a lot of the competitors in the Long Course Duathlon - a 5km run, 20km cycle and 2.5km run.
Francis and team mate Lee Harris were the first home in 59m 44s, while the individual winner was Jimmy Hildreth in 1h 8m 21s, just over a minute ahead of runnerup Adam Holmes and third-placed Paul Nesbitt.
Tonia Nesbitt was first woman home in 1h 13m 13s.
In the Kids Duathlon, which had a total of 19 competitors, line honours went to Sage Zimmerman, with Arlo Johnston runnerup and Riley Wright in third.
