Veteran Swedish sprint star Sarah Sjoestroem won the women's 100m freestyle gold medal on Wednesday, touching first ahead of American Torri Huske.
The world record holder hit the wall in 52.16secs with Huske picking up silver in 52.29 and Hong Kong's Siobhan Haughey taking bronze in 52.33.
Australia's Mollie O'Callaghan, the 200m champion, came fourth.
Huske went out hard and turned in the lead at halfway.
O'Callaghan is renowned as a fast finisher and was seen as favourite, but she failed to bring it home with Sjoestroem winning by a fingertip.
The Swede, 30, initially wasn't planning to enter the 100m.
Despite winning four Olympic medals and 25 at world championships, she had never a gold in the 100m until now.
Sjoestroem will also race the 50m freestyle.
