Top Aussie swimming coach says Chinese star's world record swim to beat Kyle Chalmers is not humanly possible: 'If it seems to good to be true, it probably is'

An elite Australian swimming coach says Chinese star Pan Zhanle's astonishing 100m freestyle world record time is not humanly possible, insisting that 'if it seems too good to be true, it probably is'.

The 19-year-old superstar broke his own mark by 0.4 of a second to demolish Aussie Kyle Chalmers, whom he finished a whole second ahead of.

The incredible effort meant a first-ever medal for China in the 100m freestyle, but swim coach Brett Hawke isn't convinced and has admitted that the swim has made him 'angry'.

'Listen, I'm just going to be honest, I am angry at that swim,' Hawke posted on his Instagram account after the race.

'Look I'm angry for a number of reasons. Look my friends are the fastest swimmers in history from Rowdy Gaines to Alex Popov to Gary Hall Jr, Anthony Irvin and all the way up to King Kyle Chalmers. I know these people intimately, I've studied them for 30 years.

'I've studied this sport. I've studied speed. I understand it. I'm an expert in it, that's what I do okay.

'I'm upset right now because you don't win 100 freestyle by a body length on that field. You just don't do it.

'It is not humanly possible to beat that field by a body length.

'I don't care what you say. This is not a race thing, this is not against any one particular person or nation, this is just what I see and what I know.

'That's not real, you don't beat that field. Kyle Chalmers, David Popovici, Jack Alexy, you don't beat those guys by one full body length in 100 freestyle. That's not humanly possible okay so don't sell it to me, don't shove it down my throat. It's not real.'

Hawke, who is also a former Olympic swimmer himself, also posted a message to his Instagram story that read: 'If it seems too good to be true, it probably is'.

He did not mention doping directly, but China's team has been under increased scrutiny since revelations 23 swimmers tested positive to a banned substance before the Tokyo Olympics three years ago.

Pan was not in the group of 23 which was allowed to compete in Tokyo after world anti-doping authorities accepted China's explanation the swimmers had eaten contaminated food at a team hotel.

Chalmers believes his Chinese conquerer is drug-free after the Australian swim ace was beaten to another Olympic title in Paris.

Asked after the race if he was worried about Pan's stunning swim being tainted by rumours Chinese swimmers have been doping, the Aussie was clear-cut in backing his rival.

'I do everything I possibly can to win the race and trust everyone's doing the same as I am, staying true to the integrity of sport,' silver medallist Chalmers said.

'I trust that ... he [Pan] deserves that gold medal.'