Caeleb Dressel grabbed a hat-trick of gold medals and normal service was resumed for Katie Ledecky on a great day for American swimmers at the World Aquatic Championships.
Dressel took his medal tally for the competition to seven - all but one being gold - and also played his part in the USA setting a world record in the 4x100m mixed freestyle relay in Gwangju on Saturday.
The 22-year-old was crowned 50m freestyle champion with a championship-record time of 21.04 seconds, as Bruno Fratus of Brazil and Kristian Gkolomeev of Greece shared the silver medal.
Dressel was too quick for his rivals again in the 100m butterfly final, missing out on bettering the new world record he set on Friday, but taking gold in a time of 49.66.
Hungary's Kristof Milak could only finish fourth three days on from setting a new world record in the 200m fly, with Andrei Minakov taking silver for Russia and Chad le Clos of South Africa earning bronze.
Dressel, Simone Manuel, Mallory Comerford and Zach Apple then combined to put their names in the record books with a world-record relay victory, triumphing in 3:19.40 ahead of Australia and France.
Ledecky withdrew from the 200m freestyle due to illness after having to settle for 400m freestyle silver, but the 22-year-old great retained her 800m freestyle crown on the penultimate day of competition in South Korea.
Regan Smith also did team USA proud, winning the 200m backstroke title on a day in which Sweden's Sarah Sjostrom was the only non-American gold-medal winner - touching the wall first in the 50m butterfly.