Full coverage: 2016 Rio Olympics

In Olympic swimming, the U.S. were strong favorites in the men’s 4x100m freestyle relay, especially with flagbearer Michael Phelps on the squad.

The most decorated Olympian of all-time put his team ahead in the second leg, before the Americans hung on to win the title. This is the 19th gold medal of Phelps career, and 23rd overall. That performance brought an end to a busy day at the pool.

Swimmers from the United States of America attend the awarding ceremony of the swimming final of men's 4x100m freestyle relay at the 2016 Rio Olympic Games in Rio de Janeiro, Brazil, on Aug. 7, 2016. The United States won the gold medal with 3 minutes 9.92 seconds.（Xinhua/Wang Peng）

Earlier in the women’s 400-meter freestyle, U.S. swimmer Katie Ledecky entered as the clear favorite, and leads for most of the race. She finished in 3 minutes, 56.46 seconds, her second world record of the day, after earlier doing so in the heats. Jazz Carlin of Great Britain took second.

In the women’s 100m butterfly, China’s Chen Xinyi and Lu Ying would challenge three-time world champ Sarah Sjostrom. The Swede dominated, and touched the wall first in 55.48 seconds, a new world record. Canada’s Penny Oleksiak came in second.

And in the men’s 100-meter breaststroke, Adam Peaty of Great Britain would break the world record he set in Saturday’s semifinal. Peaty finished in 57.13 seconds, 1.56 seconds ahead of the runner-up, South Africa’s Cameron Van der Burgh.