CANBERRA, April 6 (Xinhua) -- Former swimming world champion Grant Hackett has made an impressive comeback by qualifying for the World Championship in Russia on July at Australia's National Championship Sunday.

Hackett clocked 1:46.84 to finish fourth in the 200-meter freestyle final and earned a relay berth for July's world titles in Kazan, Russia.

The 34-year-old dual world champion achieved the mission impossible with just six months' training after a six-year break.

"If you had asked me 10 years ago if the only thing that got me on the team was on the relay it would be bitter disappointment, but right now, it is one of the biggest achievements of my life," Hackett said.

It was revealed last year that Hackett has been seeking treatment for sleeping pill addiction.

Also at Sunday's event, Mitch Larkin clocked 53.10, his personal best, claiming the 100m backstroke final in the fastest time in the world this year.

It would have claimed silver at the 2013 world championships.