Michael Phelps led the USA's 4x100m freestyle relay team to victory in the World Championships in Melbourne.
Phelps and Manaudou are both going for eight golds
Phelps helped the American quartet post a time of three minutes 12.72 seconds to finish ahead of Italy and France.
France's Laure Manaudou, who is also going for a record gold target, easily won the 400m freestyle with the second fastest time in history.
The men's 400m freestyle saw South Korea's Park Tae-hwan beat Australian Grant Hackett.
Park clocked a time of 3:44.30, with Tunisia's Oussama Mellouli in second and Hackett back in third.
Manaudou had originally entered nine events but dropped out of the 200m individual medley to concentrate on the 400m world record.
The 20-year-old led from start to finish and the victory over Otylia Jedrzejczak of Poland in second and Japan's Ai Shibata in third was just 0.48 seconds outside the world record she set last year in Budapest.
She said: "I wanted to exceed my own expectations so I prepared for this competition intensely, so (the lead) came from that preparation."
Britain's Jo Jackson recorded a personal best in the same race of 4:07.42 to claim a creditable seventh place. The 20-year-old from the Derwentside club went out hard and was third at the halfway stage before fading down the stretch.
"I'm disappointed I didn't go quicker," said Jackson afterwards. "I'm still learning and I know there's more to come."
I am not surprised with Park - he has worked very hard and is obviously a force to be reckoned with
Park's shock 400m freestyle victory owed much to a blistering last lap.
It is the first time a South Korean has won a world swimming title and Hackett admitted the 17-year-old would be a big threat in the 1500m.
"I am not surprised with Park. He has worked very hard and is obviously a force to be reckoned with," he said.
The home crowd, packed into the Rod Laver Arena, got some cheer when they saw the Australian women's 4x100m freestyle team win with a new championship record of 3:35.48.
The United States were second (3:35.68) and the Netherlands third (3:36.81).
Britain's quartet of Fran Halsall, Mel Marshall, Julia Beckett and Ros Brett gave a decent performance in the morning heats to qualify for the final in eighth place but could not improve on that in the final.
The men's 4x100m team finished ninth in a new British record of 3:41.28.
Elsewhere, Germany's Britta Kamrau-Corestein took gold in a weather-affected race for the women's 25km open water title.
The race was halted on Saturday because of heavy seas but Kamrau-Corestein held on to win ahead of America's Kalyn Keller and Russia's Ksenia Popova.
In the men's event, Yury Kudinov took Russia's fourth open water title in winds in excess of 22mph.
He finished ahead of Italy's Marco Formentini and Egypt's Mohamed Zanaty.
In the diving pool, Gleb Galperin ended China's domination by winning the men's 10m platform world title ahead of Zhou Luxin.
Galperin amassed 554.70 points to upset Zhou who finished second with 519.15. Zhou's Chinese team-mate Lin Yue was third with 513.70.
In the women's 3m springboard China's Guo Jingjing won a record fourth consecutive title.
Swimming's international governing body Fina handed Russian world swimming champion Anastasiya Ivanenko a two-year ban on Sunday for failing a doping test.
The 18-year-old, who tested positive for a diuretic in January, said her grandmother had given her the substance after she felt sick.
Ivanenko won the women's 800 metres freestyle title at last year's world short course championships in Shanghai.