U.S. swimmer Dana Vollmer won the women's 100 meter butterfly on Sunday, setting a new world record in the process.
Vollmer won in 55.98 seconds, shaving eight hundredths of a second off Sarah Sjostrom's former mark.
Alicia Coutts of Australia claimed the silver in 56.87, with China's Lu Ying taking bronze a split second back.
Vollmer, a 2004 Athens gold medalist in the 4 x 200m freestyle, had set an Olympic record of 56.36 seconds in the heats and lead the final from the front to win comfortably.
Sweden's Sjostrom had to settle for fourth.
