Keep quiet. And think strategically.

The 18-year-old is now a Commonwealth record holder, setting a fresh benchmark in the 200m freestyle at the national titles in Adelaide on Tuesday night.

Titmus was Australian swimming's shooting star last year, winning swags of medals at the Commonwealth Games, world short-course and Pan Pacifics.

Now, she's entering an 16-month block which could define her swim career - world championships in July, then the 2020 Toyko Olympics.

Titmus has already plotted her path. And it revolves as much about mental deeds as physical.

"I'm swimming faster than I have ever have before so I feel like I had that in me," she said of her Commonwealth record time of one minute 54.30 seconds.

"I just had to make sure I had my head on. I knew if I wanted to swim that quickly, it would all be mental."

Meaning?

"I feel like when I race, I perform when I'm really focused and don't really talk to anyone," she said.

"I'm usually known as quite a chatty person and it distracts.

"I have to make sure if I want to race fast that I try and internalise."

Titmus said she was now excited at the prospect of racing after a full taper - she swam in Adelaide after only two days' rest.

That will come at the July world championships and next year's Olympic, where she will race freakish freestyler Katie Ledecky from the United States.

Ledecky is the world record holder over 400m, 800m and 1500m but Titmus - who races the 200m, 400m and 800m - was already scheming.

"Katy I think will have the 800 covered at the Olympics, she is just that far ahead," she said.

"Whereas the 200 and the 400, I think I'm a bit more in the mix.

"I will focus on the three distances but I think for my 400, focusing on the 200 more than the 800 will help me a bit more."

Australian Associated Press