Kazan (Russia) (AFP) - Katie Ledecky wrote more swimming history at the world championships on Saturday by breaking her own 800m freestyle record and claiming an historic fifth gold medal.
The 18-year-old became the first swimmer to sweep the world titles for the 200, 400, 800 and 1500m freestyle, while she also won gold in Kazan in the 4x200m freestyle relay.
She clocked eight minutes, 07.39 seconds over 800m to shave 2.61secs off the record she set last year.
It was a mark of her dominance that New Zealand's Lauren Boyle set a new Oceania record of 8:17.65 to take silver, but still finished 10.26secs behind Ledecky.
Having twice lowered her 1500m mark here, this was the third time American Ledecky broke a world record in Kazan, and the 10th time in her career.
She holds the hat-trick of records in the 400, 800 and 1500m freestyle as world records have now fallen on 12 occasions in Kazan.
Having won four gold medals at the Barcelona world championships two years ago, Ledecky has gone one better in Kazan and thrived despite a punishing schedule here.
"I couldn't be happier with how that swim went or how the whole meet has gone," beamed Ledecky.
"This one was very special in as much as the fatigue I could have got, so today shows that I can manage my schedule really well.
"I don't really think about the historical aspects during the meet, but I guess I can now and I will cherish these moments."
- Phelps challenge -
South Africa's Chad le Clos avenged his defeat in the 200m butterfly final earlier in the week by retaining his 100m world title -- then threw down a cheeky challenge to US star Michael Phelps.
Le Clos clocked 50.56 seconds for a new African record in the 100m final as Hungary's Laszlo Cseh finished second at just 0.31 back.
It was sweet revenge as Le Clos, the 200m Olympic champion, lost his world crown on the wall over the same distance to Cseh in Wednesday's final, when he was edged out by just 0.20.
Phelps clocked a stunning 1min 52.94sec to win the 200m butterfly at the US championships in San Antonio, Texas.
Having beaten Phelps on the wall to deny the American the 200m butterfly gold at the 2012 London games, Le Clos said he is relishing their showdown at the 2016 Rio de Janeiro Olympics.
"I'm very excited for Rio next year and I hope he's in good shape, because I'm in good shape and when Chad le Clos comes at you in the last 50m, you'd better be ready," grinned the South African.
"It's going to be another great battle in Rio and I'm looking forward to another fight like it was at London 2012."
Missy Franklin ended her wait for gold in Kazan by anchoring the USA to mixed 4x100m freestyle relay victory in a new world record time.
Franklin touched the wall at three minutes, 23.05 seconds, just 0.05secs ahead of Femke Heemskerk as the Netherlands took silver while Canada claimed bronze at 0.54.
Having finished the 2013 Barcelona world championships with six golds two years ago, this was Franklin's first win in Kazan after silver in the 200m backstroke, plus 200m freestyle and 4x100m freestyle relay bronze medals.
The gold made up for losing her 200m backstroke world crown to Emily Seebohm, who completed a unique backstroke double for Australia.
Seebohm, who won the 100m world crown on Tuesday, matched compatriot Mitchell Larkin, who achieved the men's 100 and 200m backstroke double.
Having also won a relay gold, Seebohm's hat-trick is all the more remarkable as she split from her coach just after the Australian trials in April and dislocated her knee in a freak horse riding accident in May.
Sweden's Sarah Sjostrom became the first female swimmer to win both butterfly sprint titles at a world championships when she added the 50m crown to her 100m title.
The 21-year-old Sjostrom has now won three medals in Kazan, having also collected a silver in the 100m freestyle, and twice broke the 100m butterfly record en route to winning the final last Monday.