Updated July 24, 2017 08:16:26

Photo: Titmus swam a personal best in the 400m in Budapest. (Supplied: Australian Dolphins Swim Team)

Tasmanian swimming sensation Ariarne Titmus has finished fourth in the 400 metre event at the FINA World Championships in Hungary, marking her arrival on the world stage.

The former Launceston student qualified third fastest in the preliminary final, swimming a personal best time of 4:04.26.

She clocked the exact same time in the final, where she claimed fourth spot behind 11-time world champion Katie Ledecky of the United States.

Ledecky swam 3:58:34, two seconds behind the world record she set at last year's Rio Olympics.

Titmus has had a meteoric rise, only making the Australian junior team last year and this year moving up to the Australian Dolphins Swim Team.

"I did want to go a bit faster, but I think having to push the heats this morning a lot harder than I'm used to kind of took it out of me," Titmus told Swimming Australia.

"I've got to get used to doing that when I'm racing best in the world."

Photo: Ariarne Titmus catches her breath after winning the 400m freestyle at the national titles in April. (AAP: Greg Hunt)

Her father Steve Titmus said he was "still pinching himself" at his daughter's success.

"Fourth in the world, as a 16-year-old swimming against other swimmers who are aged 20, 22, 25 years of age ... we're just daydreaming," he told ABC Radio Hobart.

Mr Titmus said being a parent and watching his daughter's rise has been "extraordinary".

"Watching our daughter, at 16 years of age, swim at the world championships on a stage that's got some of the greats of the world is really surreal."

Titmus, who won her first senior international race at the French Open earlier this month, is now fourth on the all-time Australian any-age rankings.

Swimming Australia said Titmus was "one to watch".

The family moved from Tasmania to Queensland two years ago so Titmus could access more elite competitions and training, but her father said she was still a Tasmanian at heart.

"You can take someone out of Tassie but you can't take the Tasmanian out of someone," he said.

"Ariarne still calls herself a Tasmanian and we certainly do."

Mr Titmus said his daughter's ranking was a sure sign of the swimmer's bright future.

"Now it's verified that she's ranked fourth in the world ... she's set herself up beautifully for the Commonwealth Games next year and of course more world championships ... and eventually the Olympic Games in Tokyo."

Photo: Ariarne's family was poolside in Budapest supporting the 16-year-old. (Supplied: Australian Dolphins Swim Team)

Topics: swimming, sport, tas, launceston-7250, hungary

First posted July 24, 2017 08:14:20