Stubblety-Cook surprised himself when he swam the fastest 200 metres breaststroke ever in Adelaide on Thursday night.

But the 23-year-old says there's room for improvement on his record-breaking victory at the Australian championships.

How much more?

"I am not sure," Stubblety-Cook said.

"I am probably much more process driven than outcome driven.

"But I think I can continue to build that front-end a bit more.

"And we have spoken about it, doing a bit more 100 (metre) work and building through that (first) 100 a little bit quicker."

Stubblety-Cook won in two minutes 05.95 seconds, besting the previous benchmark of 2:06.12 set by Russian Anton Chupkov in 2019.

And the Brisbane-born athlete, who won gold in the event at last year's Olympic Games, was banking on being driven faster by stiffer competition at next month's world titles in Budapest.

"When I race in a world-class event at a world champs it will be even better," he said after beating Matt Wilson by 4.19 seconds in Adelaide.

Stubblety-Cook said he was largely unaware he was on world-record pace until well into the final lap.

"I didn't think we were going that fast," he said.

And nor could he instantly grasp the magnitude of his achievement.

"It's a lot to wrap your head around," he added.

"It's a bit surreal to be perfectly honest.

"I was obviously hoping to swim fast and hoping to swim close to my best.

"But that is just something else."

Australian Associated Press