Ian Crocker demolished the world record to win the 100 metres butterfly at the world swimming championships on Saturday and ruin Michael Phelps's dream of winning six gold medals.

Crocker stormed through two laps of the Montreal pool in 50.40 seconds to wipe 0.36 off the previous mark which he set at last year's U.S. Olympic trials at Long Beach, California, and retain the world title he won at Barcelona in 2003.

Phelps was unable to match Crocker's incredible burst of speed and had to settle for second place in 51.65 while Ukraine's Andriy Serdinov was third in 52.08.

"I always assume that whenever I race against Michael it's going to take something amazing like a world record to win," Crocker said. "It's definitely faster than I thought I could go but you can't put limits on yourself."

Crocker's win helped erase some of the lingering pain from his gut-wrenching loss to Phelps in last year's Olympic final when he led all the way but misjudged his touch on the wall, allowing Phelps to sneak through.

It also destroyed Phelps's bid to match Ian Thorpe's record haul of six gold medals at a single world championship. Phelps will still leave the meet as the most decorated athlete with at least four gold medals and a silver but his modest return of two golds and a silver from his five individual events has given him real cause for concern.

"This year, this world championships has been a big wakeup call," he said. "What happened here I'm going to use as motivation in the coming year to get back to my best times."

Leisel Jones collected her third gold medal on Saturday as part of the Australian team that won the women's 4x100m medley relay while her 17-year-old compatriot Danni Miatke won her first world title.

Miatke, who left her family in Darwin three years ago to move to Melbourne in the hope of carving out a career as a professional swimmer, upstaged Swedish world record holder Anna-Karin Kammerling to win the 50m butterfly final in 26.11.

South African sprinter Roland Schoeman, Zimbabwean backstroker Kirsty Coventry and American long-distance swimmer Kate Ziegler all won their second gold medals of the championship.

Schoeman hauled himself off his sick bed to power his way down the pool in 21.69 to win the 50m freestyle splash and dash with the second fastest time in history, just 0.05 outside Alexander Popov's world record.

Duje Draganja of Croatia finished second in 21.89 while Bartosz Kizierowski of Poland was third in 21.94 but neither could keep up with Schoeman, who set a world record to win the 50m butterfly earlier this week and was second in the 100m freestyle final.

"Last night I felt like I was dead so I said some prayers before going to bed asking God to care of me and make me feel better," Schoeman said.

"I did feel better but not enough to go 21.69, which is not too bad."

Coventry broke her own African record to add the 200m backstroke title to her earlier win in the 100m, leading all the way to reach the finish wall in 2:08.52. American Margaret Hoelzer finished second in 2:09.94 while Japan's [Images] Reiko Nakamura was third in 2:10.41.

"I have got to a point where I am not nervous before my events," said Coventry, who also won the 200m Olympic title last year. "I'm not freaking out that this is the world championships."

Ziegler, 17, also produced a bold front-running display to win the 800m freestyle in 8:25.31 following her runaway victory in the 1500m won earlier this week.

Canada's [Images] Brittany Reimer finished second in 8:27.59 while Japan's Olympic champion Ai Shibata was third in 8:27.86.

Jones, who the 100m-200m breaststroke double earlier in the week, teamed up with Sophie Edington, Jessicah Schipper and Libby Lenton to win the medley relay for Australia in a combined time of 3:57.47, just 0.15 outside the world record Australia set at last year's Athens Olympics [Images].

The U.S. finished second in 3:59.92 after leading for the first 150m while Germany [Images] were third in 4:02.51.