Australia sits atop the medal tally of the Rio Olympics after claiming two gold medals in the pool on day one of the event.
Australia's women retained their Olympic title by winning the 4x100m freestyle relay in world record time, with sisters Bronte and Cate Campbell swimming the last two stages to overhaul the United States, despite the efforts of Katie Ledecky on the anchor leg.
Mack Horton's victory in the men's 400 freestyle also meant Australia had already doubled their gold medal tally from a disappointing showing four years ago.
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.