Full coverage: 2016 Rio Olympics

Australia's Mack Horton wins men's 400-meter freestyle

The first day of swimming has just concluded in the Olympic Aquatics Stadium. China's Sun Yang came in as the defending champion in the men's 400-meter freestyle, and he carried heavy expectations to repeat, and win the first gold medal for the country at these Summer Games -- not to mention being the only Chinese swimmer to reach the finals on Day One.

Sun is also the reigning champion in the 1500m freestyle, and in his first final race in Rio, he would be up against strong opponents such as Mack Horton of Australia, and James Guy of Great Britain.

Horton and Sun are neck in neck in the last 100 meters. But it's Horton who touches the wall first in three minutes, 41.55 seconds, with Sun only 13 hundredths of a second behind to capture the silver medal.

Guy gets off to a good start and he would hold on to remain in the lead after 250 meters. Horton and Sun speed up after that with the Australian taking over the lead after the next turn with Sun just behind him.

Horton and Sun are neck in neck in the last 100 meters. But it's Horton who touches the wall first in three minutes, 41.55 seconds, with Sun only 13 hundredths of a second behind to capture the silver medal.

Hungarian sets new world record in victorious time of 4:26.36

Five-time world champion Katinka Hosszu set a new world record in the women's 400 meter individual medley final after finishing in a time of four minutes, 26.35 seconds, beating Maya Dirado of the USA, and Spain's Mireia Belmonte Garcia.

USA’s Chase Kalisz & Japan’s Daiya Seto complete podium

In the men's individual medley, Japan's Kosuke Hagino, the bronze medallist from the London Olympics, shows his speed and claims the first gold medal for Japan in a time of four minutes, 6.05 seconds. USA's Chase Kalisz and Daiya Seto of Japan comes in second and third.

China’s Li Xiang makes it into men’s semi-finals in event

Adam Peaty of Great Britain demolishes his own world record in the heats of the 100-meter breaststroke as he launches a bid to become the first British man to win an Olympic swimming gold medal for 28 years. China's Li Xiang also reaches the semi-finals after finishing 11th in the heat.