Three swimming world records were broken on Friday at the FINA World Aquatics Championships in Gwangju, South Korea. One of those was set in the semifinal of the men's 100-meter butterfly by Caeleb Dressel of the U.S., who bested the 2009 mark of his rather well-known compatriot Michael Phelps.

Dressel, who won seven world titles in Budapest two years ago, was in lane 4. The 22-year-old American had already won gold in the 50-meter butterfly, 100-meter freestyle, and the 4x100-meters freestyle relay, and his time of 49:50 broke Phelps' record of 49:82 and made him the favorite to win a fourth gold.

In the women's 200-meter backstroke semifinals, Regan Smith of the United States also set a world record. The 17-year-old beat the world junior time of 2:06:01 in the heats before she touched home first at 2:03:35, well under compatriot Missy Franklin's record of 2:04:06 from the 2012 Summer Olympics.

The day's third world record was set Russia's Anton Chupkov in the men's 200-meter breaststroke final. Chupkov was fifth after 150 meters but moved into the lead down the stretch and finished at 2:06:12 to beat the previous record set in 2017 by Ippei Watanabe of Japan. Matthew Wilson of Australia touched in 2:06:68 to win silver while Watanabe bagged the bronze.

Chinese athletes were led by Sun Yang who won two golds in the individual events in the men's 4x200-meters freestyle relay final. The Chinese were hoping for a spot on the podium, but came up well short in a disappointing result.

China was in Lane 2 and their first swimmer was Ji Xinjie. Australia and USA were title contenders in this event, but Ji didn't let his teammates down remaining in second place after the first 200 meters, just behind Britain.

Wang Shun was China's second to go but he was unable to keep the team's position and fell out of the top three after the halfway point while British swimmers stayed in control, followed by the Americans and Australians.

Backstroke star Xu Jiayu swam the third leg for China. The reigning 100-meter backstroke champion joined the relay instead of sticking to the 200 meters backstroke. His result in the freestyle final was second slowest of the 32 swimmers and when he handed over to Sun, China was down to sixth.

That left little hope of a podium finish. Even though Sun gave everything he had, the 27-year-old was unable to make up any ground and China ended up in sixth place in 7:04:74. Australia won gold in 7:00:85 while Russia and USA were second and third respectively.

"I've already tried my best. We could say that we did our best today, even though it was really hard to catch up from behind with strong waves in the pool. It was a test for me because I swam nearly 4,000 meters in five days. I hope to inspire myself and my teammates with my persistence," Sun said.