Gabrielle Fa'amausili has successfully defended her title with a superb swim at the Fina World Junior Championships in Singapore.
In a battle between the 15-year-old stars of the future, Fa'amausili edged out Australia's Minna Atherton by of a second to claim the gold medal in the 50m backstroke final.
The United club swimmer from Auckland repeated the title she won two years ago in Dubai.
She managed to turn the tables on Atherton, who had won the 100m and 200m titles earlier in the meet, and set a new junior world record in the 50m in the semifinal.
Fa'amausili won in 27.81s, which is the eighth-fastest time overall in the world this year and breaks her New Zealand open record, going under the 28-second mark for the first time.
"It feels just amazing. I just can't believe the result and I am just super happy with it," Fa'amausili said.
The teenager, who took more than 03.s off her previous best and national record, said much of the credit must go to her new coach Igor Polianski, the 1988 Olympic backstroke champion and a double world champion.
"I am so thankful for all the work that my new coach has done with me over the last two months because he has given me the confidence to do two swims back-to-back. With all that knowledge and confidence I was able to go out there and win for me, for my country and my family."
Fa'amausili had swum the semifinal of the 50m freestyle 30 minutes before her backstroke final, finishing 10th fastest in 25.86s.
Her compatriot Bobbi Gichard, who won the bronze medal in the 100m backstroke final, finished fourth in the 50m final in 28.40s, which lowered her personal best for a second time at the meet.
New Zealand high performance development coach Donna Bouzaid said the two 15-year-old backstrokers were outstanding prospects, and both would be strong candidates to push for qualification for next year's Rio Olympics and beyond.
Bouzaid said they would lead an exciting group of talented young swimmers who would target the 2020 Tokyo Olympics.
The New Zealand team's campaign at the junior world championships finishes tomorrow with North Shore's Yeonsu Lee and United's Annabelle Paterson competing in the 200m freestyle.