Canada's Chloe Isaac performs during the solo free event on Thursday in Rome. (Gregorio Borgia/Associated Press)

Chloe Isaac narrowly missed winning Canada's third synchronized swimming medal at the world aquatics championships in Rome on Thursday.

The Brossard, Que., resident had to settle for fourth in the solo free competition, behind home favourite Beatrice Adelizzi, who won bronze.

Brossard won bronze a day earlier with Canada's free combination team.

Natalia Ishchenko won Russia's fourth synchro gold medal out of five events so far at the competition. Russia is perfect in the synchro pool, as it didn't enter the free combination.

But the silver medallist didn't agree with the final standings.

Spain's Gemma Mengual, who finished half a point back of Ishchenko with a score of 98.333, sobbed on the podium as she received her silver medal.

"I hope one day the judges understand that people expect fair and accurate judgments from them," said Mengual.

Judging has long been an issue in synchro, which is dominated by Russia and leaves some believing no matter how well they perform, they stand little chance of winning.

Ishchenko performed to Tchaikovsky's Swan Lake to capture her second gold medal of the championships, adding to her solo technical title.

"I am very happy with my performance," Ishchenko said. "Only at the end of my exercise did I realize I had won the gold medal. My performance was perfect, and this is the result of a lot of training and commitment."

Mengual, who performed to Ray Charles's version of The Beatles' Yesterday, was upset that her marks for artistic impression (9.8) were lower than the ones for technical merit, where she matched Ishchenko.

"I was more confident than [the preliminaries] and I felt the crowd supporting me a lot," Mengual said. "The problem is still how the judges evaluate our performances.

"My strength is the artistic impression, and I can't understand how this was evaluated of lower quality than the technical merit."

The competition was a two-woman race that left Italy's Adelizzi and Canada's Isaac fighting for bronze.

Adelizzi's victory pumped up the home crowd at the Foro Italico.

"I still can't believe I won this medal," Adelizzi said. "I really gave it all I had. I would like to thank the crowd for their warm support."

U.S.A. wins appeal for open water bronze

Also Thursday, USA Swimming won an appeal to allow 10-kilometre open water swimmer Francis Crippen to retain the bronze he won in the event a day earlier.

FINA upheld the appeal after the Italian team protested Crippen's bronze medal performance since he swam outside the ropes en route to the finish.

The Italians were hoping the appeal would bump up their own Valero Cleri from third to fourth. German Thomas Lurz won the race and American Andrew Gemmell placed second.

Meanwhile, in the women's three-metre synchronized diving preliminaries, China's Guo Jingjing and Wu Minxia dominated to set their team up to win their fourth world title.

With nine world championship titles to her name, Guo will attempt her fifth consecutive win in synchro on the springboard on Friday. If successful, it will be her fourth as Wu's partner. The duo won gold at the last two Olympics.

The pair posted the highest marks for each of the five rounds on Thursday, totalling 342.90 points.

In second place was Italy's Tania Cagnotto and Francesca Dallape, with 316.20 points. Taking third place was Russia's Julia Pakhalina and Anastasia Pozniakova with 305.49.

Jennifer Abel of Laval, Que., and Montreal's Melanie Rinaldi were fifth with 302.70.

With files from The Associated Press