American Aaron Peirsol beat his own 200m backstroke world record on the way to winning the event at the Pan Pacific Championships in British Columbia.
Peirsol has posted nine of the 11 fastest times in the event
Peirsol beat compatriot Michael Phelps to set a time of one minute, 54.44 seconds - breaking his own record by more than two-tenths of a second.
Peirsol has not lost a 200m in international competition since the 2000 Olympic Games in Sydney.
Meanwhile the US 4x100m freestyle relay team set a new world record of 3:12.46.
The quartet of Phelps, Cullen Jones, Neil Walker and Jason Lezak eclipsed South Africa's previous record of 3:13.17 set at the Athens Olympics in 2004.