Australia sits atop of Rio Olympics medal tally after claiming two gold medals in the pool on day one of the event.
The country's 4x100 women's relay swim team, made up of Emma McKeon, Brittany Elmslie, Bronte and sister Cate Campbell, ensured Australia defended its Olympic title.
They clocked three minutes 30.65 seconds, beating Australia's previous world-best mark set at the 2014 Glasgow Commonwealth Games.
This came an hour after Mack Horton claimed a gold medal in the men's 400-metres freestyle race.
The 20-year-old is the first Australian since Ian Thorpe in 2004 to win the Olympic 400m freestyle crown.
Horton came in ahead of defending champion Sun Yang of China, with Italy's Gabriele Detti in third.
Australia won its first Rio medal earlier in the day when archers Taylor Worth, Ryan Tyack and Alec Potts, put on a thrilling display against China, securing a bronze medal.
A last-gasp goal to Germany has denied the Matildas a crucial win at the Rio Olympics.
German captain Saskia Bartusiak drove in an 88th-minute equaliser to draw the match 20-all.
After Wednesday's shock loss to Canada, a win would have been more than useful as they attempt to progress beyond the group stage.
Australia's female basketball team have won their first game of the Rio Olympics women's basketball tournament, beating hosts Brazil 84-66.
Not since 1988 have the Opals lost the first match of an Olympic campaign - the last time they did not win a medal at a Games.
The Opals have just 24 hours before their second match against Turkey on Monday morning, Australian time.
The US and Vietnam have been among first gold medal winners on day one of the Games.
US teenager Virginia Thrasher won the first gold medal of the Games, holding her nerve against two Chinese Olympic champions to clinch the women's 10m air rifle event.
Xuan Vinh Hoang of Vietnam secured gold in the men's 10m air pistol event, holding off the heavy crowd favourite Felipe Wu of host country Brazil.
Belgian cyclist Greg van Avermaet snatched gold in a thrilling and incident-packed men's road race, out-sprinting Denmark's Jakob Fuglsang alongside the Copacabana beach.
One of the best Olympic road races looked like it would be won by Italy's Vincenzo Nibali, but he careered out of control at speed.
Australia's Richie Porte also crashed hard on the descent, colliding with a metal pole at the side of the road. Initial reports suggested he suffered a broken collarbone.
Security scares
The first day of Olympic competition in Rio has been marred by a series of security scares.
Officials are investigating reports that a bullet tore through a tent in the media area of the equestrian centre, while the bomb squad was called in to detonate an unattended backpack at the finish line of the men's cycling road race.
According to reports, a bullet hit the press center in the Deodoro area of Rio's Olympic park, landing on the floor at the feet of journalists covering equestrian events.
"Security is investigating that incident and will make a statement later," the venue manager Anja Krabbe told Reuters, adding she was not in the tent where journalists reported hearing an object tear through the plastic.
Security remains a top concern at the Rio Games and several incidents including killings, kidnappings and robberies have kept police on alert. An officer shot and killed a 22-year-old man just a few blocks from the Maracana stadium where the opening ceremony took place.
Meanwhile, bomb squad agents in protective clothing were seen operating near an area where media were seated on the boulevard of Copacabana beach. It follows the detonation of another unattended bag near the same spot the previous evening during the opening ceremony for the Games.
A spokeswoman for the public security department said that officials believe the bag may have belonged to a homeless man, but protocol requires any unattended objects to be destroyed.
Lorie Schmetterling, who traveled from the United States with her husband Eric to cheer on their daughter Laura, who is in a rowing event, had not heard the blast but was disturbed to learn it had occurred just a few hundred meters from where she was staying.
"You hear all these terrible things about how it is going to be and then you get here and it seems fine," she said. "Then this happens and you feel it, you go on high alert again."
A security source said that officials were particularly concerned about this bag because it was close to the Russian hospitality site for the Games.
In recent days, bomb squad members have detonated several unattended bags in controlled explosions around Rio amid high security.
Brazil detained 12 people for suspected links to Islamic State last month but it has insisted that the risk of an attack at the Games is minimal.
Brazil has deployed some 85,000 police and military to guard the Games, roughly twice the number at the 2012 London Olympics.
