Open water competition at the World Swimming Championships went off Wednesday after two postponements because of water-quality problems at Sentosa, the island area on the coast of Singapore.
Florian Wellbrock of Germany won the men's 10-kilometer race in 1 hour, 59 minutes, 55.50 seconds. Gregorio Paltrinieri of Italy was 3.7 seconds behind in second place, and Kyle Lee of Australia was third in 2:00:10.3.
Moesha Johnson of Australia won the women's 10-kilometer race in 2:07:51.3. Ginevra Taddeucci of Italy took silver in 2:07.55.7, with bronze for Lisa Pou of Monaco in 2:07.57.5.
Wellbrock took gold in the Tokyo Olympics in the 10-kilometer race and was the bronze medalist at 1,500 meters in the pool. This is his eighth gold in world championship events.
"It was really tough today. I think it was the warmest waters that we've had to race in," Wellbrock said. "I had one year to prepare for this. We did a lot of heat training, and I think that was the key today to me taking the gold."
Johnson was the silver medalist in this event a year ago at the Paris Olympics. She also took gold in the 2024 Doha worlds and was the bronze medalist two years ago in Fukuoka, Japan.
The open water swimming program had been initially scheduled to open Tuesday.
Event organizers said water-quality samples taken Tuesday afternoon showed "a significant improvement with levels of E. coli falling between the ranges of good and excellent" in regulations set by the governing body World Aquatics.
The Mayo Clinic says "E. coli bacteria normally live in the intestines of healthy people and animals. Most types of E. coli are harmless or cause relatively brief diarrhea." It said a few strains can cause "severe stomach cramps, bloody diarrhea and vomiting." Exposure is often from contaminated water that may contain human and animal waste.
The open water events in the Seine River at last year's Paris Olympics were a constant cause of concern. The Tokyo Olympics also had problems in 2021 because of warm water in a shallow bay and related pollution issues.
Water pollution was a major problem in the Rio de Janeiro Olympics, where pollution levels were often high on Copacabana Beach, the venue for distance swimming, and in Guanabara Bay, the venue for sailing.
Other open water races in Singapore are set for Friday, Saturday and Sunday.
Water polo competition at the worlds is underway at an indoor venue. The main event of the championships is eight days of swimming competition in the pool, which opens July 27.
The Associated Press and Reuters contributed to this report.