Aussie swimmer caught in 'dead-heat' controversy at Olympics

Aussie fans were left gobsmacked while watching the Olympics on Saturday night when swimmer Emma McKeon appeared to touch the wall well before Chinese rival Zhang Yufei, only for the race to be declared a dead-heat.

McKeon was equal-fastest in the 100-metre butterfly heats in Tokyo, dead-heating with China's World No.1 as Australia's feted swim team opened their Olympic campaign.

EXPLAINED: Why swimming finals are being held in the morning

'HEART BREAKS': Japan in shock over devastating Olympics moment

McKeon made a slick start in her quest to join Aussie icons Shane Gould, Ian Thorpe and Alicia Coutts in collecting five medals at a single Olympics.

The 27-year-old is eyeing a seven-medal haul with her bumper program beginning with an ominous swim on Saturday night.

And even though it didn't really matter because it was just a heat, many thought McKeon should have been declared the outright winner.

The Aussie appeared to touch the wall well before Zhang, with an image circulating on social media seemingly showing exactly that.

Sports journalist Tony Harper tweeted the photo, writing: "Of course it doesn't really matter, but how did Emma McKeon not win that heat from here?"

Victorian cricket great Darren Berry tweeted: “WTF seriously Emma McKeon touched clearly ahead of China on the wall how on earth can that be a dead heat?”

Some pointed out that McKeon may have touched the wall with soft hands, meaning it took longer for the sensors to register her touch.

The wall technology in swimming requires the athletes to touch firmly in order to register the time straight away.

If McKeon touched the wall softly at first and then Zhang came in with a firm touch, it's possible for their times to register as the same.

Brendon Smith goes fastest in 400m individual medley

Meanwhile, Australia's women's 4x100m freestyle relay team - seeking a third consecutive Olympic title - cruised into Sunday's final as a 21-year-old Victorian emerged as a surprise gold medal contender.

Brendon Smith clocked an Australian record in the 400m individual medley heats to be fastest into Sunday's final.

Smith's stunning swim came as the host nation's hero, reigning medley world champion Daiya Seto, flopped and failed to make the medal race.

Australia's dominance of the women's freestyle relay continues despite the absences of McKeon and flag-bearer Cate Campbell in the heat team.

Mollie O'Callaghan, Meg Harris, Madi Wilson and Bronte Campbell still booked lane four, in a time almost two seconds ahead of the next-best, the Netherlands.

Australia's star attractions McKeon and Campbell, who hold the fastest 100m freestyle times in the world this year, will race in Sunday's final with Wilson and triple Olympian Bronte Campbell.

McKeon's relay final will follow her 100m butterfly semi-final, with compatriot Brianna Throssel sneaking into those semis as 16th qualifier.

In the men's 400m freestyle, Australians Elijah Winnington and Jack McLoughlin dead-heated for first in their heat - they're equal-fourth quickest into Sunday's final.

Australia's two 100m breaststrokers, Zac Stubbelty-Cook and Matt Wilson, couldn't advance from their heats.

with AAP

Watch 'Mind Games', the new series from Yahoo Sport Australia exploring the often brutal mental toil elite athletes go through in pursuit of greatness:

Click here to sign up to our newsletter for all the latest and breaking stories from Australia and around the world.