Saving their best until last, a Cate Campbell-inspired Australia have caused a boilover by claiming 4x100m mixed medley relay gold on the opening night of the Pan Pacs swimming in Tokyo.
Australia finally savoured victory on day one when Campbell, Mitch Larkin, Jake Packard and Emma McKeon combined to clock three minutes, 38.91 seconds - just 0.35 of a second shy of the world record.
Former world champion Campbell sealed Australia's first gold in the event with a blistering final freestyle leg of 50.93 seconds - the fastest split in history.
Hot favourites the United States - boasting world champions Caeleb Dressel and Simone Manuel as well as world-record holder Kathleen Baker - finished a shock third.
Australia had earlier collected three silver and a bronze.
World No.1 US still dominated day one, claiming five gold with Japan nabbing two.
However, Australia will no doubt be inspired for the rest of the four day meet thanks to the relay team's shock win sealed by Campbell's history-making finish.
It was also a confidence boost for Campbell, who in the final leg blew away Manuel - the woman who dethroned the Australian by claiming Rio Olympic 100m gold.
"Our coaches have been scheming over the past couple of days trying to put together the strategically fastest team - obviously they got it right," Campbell said.
"I knew it was going to be tight (finish) whether it was going to be Japan or the US on our tail.
"For me it was about keeping a cool head and swimming my race and I did that.
"Plus no one likes to be caught - I am glad I did the catching."
Former dual world backstroke champion Larkin believed their first win of the meet would lift Australia.
"It's fantastic to start off the meet really well and hopefully that momentum carries across as it has in previous years," he said.
Australia's Ariarne Titmus began the night by claiming 800m freestyle silver behind all-conquering American Katie Ledecky.
Titmus, 17, clocked eight minutes, 17.07 seconds to eclipse Jess Ashwood's 2016 national record by more than a second and hold off fast finishing American Leah Smith for second.
However, there was no stopping Olympic and world champion Ledecky, who set a championship record of 8:09.13 to claim the meet's first gold - almost eight seconds faster than the Australian.
The Dolphins added another two silver in the 100m breaststroke.
Jessica Hansen finished less than a second behind Olympic and world champion Lilly King of the United States in the women's final.
And Jake Packard was a shock men's runner-up to Japan's Yasuhiro Koseki.
Meanwhile, Jack McLoughlin claimed 1500m freestyle bronze behind American winner Jordan Wilimovsky.
In the men's 200m freestyle, Alex Graham finished fifth behind American winner Townley Haas after Australia's Olympic champions Kyle Chalmers and Mack Horton sensationally failed to qualify for the final.