Australia dominated the opening night of swimming at the Rio Olympics, while three world records were broken on Saturday.
Mack Horton took out the men's 400 metre freestyle before the women's 4x100m freestyle relay team added to his success at the Aquatics Stadium.
The relay team of Emma McKeon, Brittany Elmslie and Bronte and Cate Campbell broke their own world record, the second set on the night in Brazil.
Hungary's Katinka Hosszu was the star by smashing the world mark in the women's 400m individual medley.
Hosszu easily beat the time somewhat controversially set by China's Ye Shiwen at London 2012.
Japan's Kosuke Hagino won the first swimming medal of the Games, while Brit Adam Peaty set a world mark of his own in the heats of the 100m breaststroke earlier on Saturday.
RACE OF THE DAY
Hosszu was enormous in the 400m IM and setting a world record rarely looked in doubt.
The 27-year-old was ahead of the mark set by Ye of China for almost the entire race before proceeding to smash it by more than two seconds.
Maya Dirado came home in second but never looked like catching Hosszu, while Mireia Belmonte won bronze.
Peaty set the tone for the day by shattering the 100m breaststroke mark with a blistering time of 57.55 seconds.
Hosszu followed, before Australia's women narrowly beat the time they set in Glasgow in 2014.
"It's just crazy that I've been able to swim two seconds faster than anyone ever, ever did. It's just crazy," - Hosszu said of her incredible swim.
"I don't know if it's a rivalry specifically but more about athletes who have tested positive in the sport," - Horton said of Sun Yang, who finished second to him.
"Definitely my favourite race ever, in an Olympic final with my sister and two girls I have known since I was 12,13 years old and a gold and a world record. You can't ask for more. Every kid dreams of it, it's what we always hoped for," - Bronte Campbell said after the world record.
All eyes will be on Peaty, who looks a huge chance of breaking the 100m breaststroke world record for the second time in as many days. Katie Ledecky is also in action in the women's 400m freestyle.