[2] He is currently a single sculler, and is the reigning world bronze medal holder, a feat achieved in his debut season in the class.

Subsequently, Mackintosh attended Massey University, where he achieved a Masters of Management extramurally, also while balancing his rowing career.

[7] After a break to focus on his university studies, he was selected in the 2016 New Zealand Under 21 Team that competed in a two-regatta series against Australia.

Returning to the 2019 World Rowing Under 23 Championships, Mackintosh's crew bettered their previous performance by achieving a silver medal.

The class is not commonly competed in by New Zealand who, prior to the gold Mackintosh achieved at the Tokyo 2020 Summer Olympics, had not medalled in the event for 49 years.

Mackintosh then took a further break from rowing to focus on his studies again, but returned to the world stage in 2022, this time in the pair with fellow gold medalist Matt Macdonald.

This was a long hiatus, having not formally competed in the class since placing third in the under 17 single scull at the Maadi Cup as a schoolboy.

At the 2023 World Rowing Champions in Belgrade, Serbia, the men's single scull field was the largest to date with 48 competitors.

In the heat, Mackintosh came up against fellow new comer Simon Van Dorp from the Netherlands, with both scullers setting a strong pace with the quickest times of the day.

In the final, Mackintosh placed third, earning a bronze medal behind Van Dorp in Silver and Zeidler in Gold.