Lauren Boyle is through to her second world championship final in Kazan, Russia, but events in the 1500m heats tonight were dominated by American star Katie Ledecky.
The 18-year-old from Maryland set a world record in her heat, clocking 15min 27.71s, in eclipsing her own world mark of 15:28.36 she put up on the Gold Coast last year.
It was the second world record of the championships, after Swedish butterfly swimmer Sarah Sjostrom did the same in her 100m semifinal 24 hours earlier.
Boyle finished third in her heat, behind runaway Dane Lotte Friis, the 2011 world champion over the distance, and, narrowly, Kristel Kobrich of Chile.
Friis broke clear early in the 30-length race and was uncatchable, recording 15:54.23.
Boyle and Kobrich had a decent duel for most of the race, with Kobrich holding on to touch in 16:01.63, 1.21s ahead of the Aucklander.