Simona Quadarella regained the 1500m freestyle world title in Doha on Tuesday while the United States dominated the backstroke and Hwang Sun-Woo reached out to grab his first world title
Quadarella, a 25-year-old Italian, won her first world title in the longest pool distance in Gwangju, South Korea, in 2019, when the dominant women's middle-distance swimmer, Katie Ledecky was absent, ill.
The American has won every major 800m and 1500m since then, but with Ledecky skipping Doha ahead of the Paris Olympics, Quadarella leapt up to the top step of the podium with a dominating swim.
She finished in 15min 46.99sec, 9.63sec ahead of Li Bingjie of China with German Isabel Gose just behind in third. None of the other finalists broke 16 minutes.
Hwang, a 20-year-old South Korean, made the most of the absence of world record holder David Popovici to win the men's 200m freestyle.
After losing the lead on the third 50, the South Korean then caught American Luke Hobson in the final meters to win in 1:45.05. Lithuanian Danas Rapsys also finished fast to take second, 0.3sec behind, with Hobson third at 0.51.
Claire Curzan, a 19-year-old American, led from the start to win the women's 100m backstroke in a time of 58.29sec. She was 0.83 ahead of Australian 18-year-old Iona Anderson.
Hunter Armstrong immediately followed by taking the men's race edging his university team-mate, Hugo Gonzalez, a Spaniard by 0.2sec.
Another 19-year-old, Tang Qianting of China won the closing event of the evening, the women's 100m breast-stroke by 0.55 sec from Tes Schouten of the Netherlands. Siobhan Haughey of Hong Kong, previously a freestyle specialist, faded to third on the second 50.