World record holder Ariarne Titmus fired a warning shot on Friday to Katie Ledecky and Summer McIntosh ahead of the Paris Olympics with the fastest 400m freestyle of the year.

The reigning Olympic champion went under four minutes at the Australian championships on the Gold Coast, hitting the wall in 3min 59.13sec to remain unbeaten in the event since 2019. Titmus beat Ledecky in a thrilling final at the Tokyo Olympics then broke the American great's long-standing world record in 2022, only for Canadian teenager McIntosh to better the mark last year.