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RIO DE JANEIRO — Since when did swimming become like boxing, with trash talking, gamesmanship and confident boasts that may or may not be backed up?

Since even before the start of the Olympics, the Aquatics Centre has become a breeding ground for heated rivalries that are spilling out of the water and into the headlines of nations around the world.

Monday saw the continuation of a simmering feud between middle and long distance specialists Mack Horton of Australia and China’s Sun Yang. Horton and Sun don’t like each other, that much is patently obvious, and each is backed up by his national swimming federation and jingoistic national media, with each side delighted to add fuel to the verbal fire.

It all seems to have begun last week, during a training session ahead of the opening ceremony. It was reported that Sun yelled at Horton then repeatedly splashed water at him, which Horton ignored. When asked why he did not react, Horton said he was not in the habit of responding to “drug cheats.”

Sun, who won two golds at the 2012 Olympics in London, served a three-month drug suspension in 2014 after testing positive for the banned heart drug Trimetazidine. Horton also referenced Sun’s drug history after beating him in the 400 meters on Saturday, after which Sun wept in the pool following his second-place finish. The pair shared a handshake on the podium that was cursory at best.

“I just have a problem with athletes who tested positive and are still competing,” Horton said.

On Monday, Chinese swimming officials asked Horton to retract and apologize, while Chinese team leader Xu Qi issued a personal attack on the Australian.

“(He has) hurt the feelings between Chinese and Australia swimmers,” Xu told the Xinhua news agency, adding that Horton’s behavior displayed a “lack of good manners and upbringing.”

The Chinese press went on the offensive too, treating the storyline as one of the biggest news items of the Games so far. In a biting editorial, Communist newspaper the Global Times savaged Horton, and then laid into his country.

“In many serious essays written by Westerners, Australia is mentioned as a country at the fringes of civilization,” the newspaper wrote. “In some cases, they refer to the country’s early history as Britain’s offshore prison. This suggests that no one should be surprised at uncivilized acts emanating from the country. We should think the same way.”

It seems Chinese newspapers do things a bit differently to what we’re used to, but it’s all good, amusing, Olympic-style fun, isn’t it?

However, Australia is not a sporting nation that likes to take a backwards step and it will be fascinating to see how this battle plays out. Australian swimming chiefs responded to their Chinese counterparts by praising Horton for his stance.

“He has spoken out in support of clean athletes,” an Australian Olympic Committee spokesperson said. “This is something he feels strongly about and good luck to him.”

Perhaps there is something in the Rio air that is making things a bit feisty down at poolside. American Lilly King is wrapped up in her own personal feud with Russian rival Yulia Efimova, a confirmed drug cheat, trash-talking her rival and swapping Dikembe Mutombo-style finger wags on Sunday.

That duo was set to meet again on Monday night, but fans will have to wait for next Sunday to see Horton and Sun square off, in what promises to be an epic 1,500-meter duel.

Sun has cranked up the boasts already, saying that despite Horton’s success so far, he is “the king” over the longer distance. Either way, the war of words is likely to continue, as the water reaches boiling point in Rio.