American star Michael Phelps won his fourth gold at the World Championships in Melbourne on Thursday with his third world record of the week.
Phelps is said by many to be the best swimmer in history
Phelps raced home in one minute 54.98 seconds to win the men's 200m medley.
Fellow American Ryan Lochte was second while Hungarian Laszlo Cseh set a European record on his way to third.
There was a dead-heat in the final of the 100m freestyle as Canadian Brent Hayden and Italy's Filippo Magnini tied for gold.
In a blanket finish the pair touched home in 48.43 seconds, edging out Australia's Eamon Sullivan.
World record holder Pieter van den Hoogenband could only finish sixth.
Leila Vaziri equalled her own world record as she won the women's 50m backstroke final in 28.16 seconds.
I'm happy with how I swam - it felt smooth and controlled and I feel there's more to come
And in the final race of the day the American quartet produced the 10th world record of the championships as they stormed to victory in the women's 4x200m freestyle.
They beat the old mark by just under three quarters of a second, winning in 7:50.09, while Great Britain were nearly seven seconds behind in fifth.
Australia's Jessicah Schipper held off a late challenge from American Kimberly Vandenberg to win the women's 200m butterfly final in 2:06.39.
Britain's 4x200m women's relay team set a new national record in the final of the event, which was won by the USA in a world record time.
The USA quartet finished in 7:50.09 ahead of Germany and France with the GB quartet of Caitlin McClatchey, Mel Marshall, Fran Halsall and Jo Jackson in fifth with a time of 7:57.02.
Kirsty Balfour was the stand-out individual British swimmer on Thursday, qualifying second fastest for the 200m breaststroke final in a time of 2:25.45.
I paid for going out too fast over the first 100m
"I'm happy with how I swam - it felt smooth and controlled and I feel there's more to come," said Balfour.
James Goddard and Gregor Tait both qualified for the final of the men's 200m backstroke but they could only post the sixth and eighth-fastest times.
Kristopher Gilchrist and James KLirton both failed to qualify for the men's 200m breaststroke finals while Francesca Halsall missed out on reaching the women's 100m freestyle.
"I paid for going out too fast over the first 100m," said Gilchrist. "It wasn't good enough - it's that simple."
World record holder Brendan Hansen has pulled out of the men's 200m breaststroke final on Friday because of a stomach virus which left him doubled up in pain.
Hansen became the most successful breaststroke swimmer in World Championship history when he retained his 100m title on Monday.