Germany-based Vivienne Rignall broke her own New Zealand record in the women's 50m freestyle heats yesterday to qualify for the semifinals.
Rignall, 26, clocked 25.52s to touch fourth in her heat, which was won by world recordholder Inge de Bruijn in an Olympic record 24.46s.
Rignall's previous record was 25.85s, set at the German championships this year.
She qualified seventh-equal for last night's semifinals, giving herself every chance of becoming New Zealand's first swimming finalist at these Games.
Rignall was delighted to have improved her personal best by 0.35s.
"It is a huge PB. If I'd done five hundredths of a second better than my PB I would have been happy because hundredths of a second can make a big difference in the 50m," she said.
She thought she had made just a little mistake right at the start, although New Zealand coach Brett Naylor told her, despite that, she had moved swiftly out of the blocks.
Dunedin distance swimmer Jonathan Duncan was well below his best time when finishing fourth in his 1500m heat in 16m 3.41s. Juan Carlos Piccio won easily in 15m 51.57s.
Duncan was 37th-fastest swimmer in the 1500m heats.
Australian Olympic champion and world recordholder Kieren Perkins was the top qualifier with 14m 58.34s.