Aussie star upstages Sun Yang for incredible slice of swimming history

He may be named after an orangutan in a Clint Eastwood movie but Australia's Clyde Lewis is clearly not monkeying around in the 200m freestyle at the world swimming titles in South Korea.

Known for his medley expertise, Lewis has remarkably upstaged world champion Sun Yang of China to emerge from lane one in the semi-finals as the top qualifier - and one of the fastest of all-time - for Tuesday's 200m medal race at Gwangju.

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He took almost a second off his person best to clock a stunning one minute, 44.90 seconds, ranking him in the 200m top 10 all-time list and second only in Australian history to the great Ian Thorpe.

"That was sick. I was out there in lane one by myself," Lewis said.

Besides claiming a 400m IM Commonwealth Games gold last year, the unheralded Lewis' biggest claim to fame to date had been his name's unusual inspiration.

His father came up with the idea of Clyde after being a big fan of the orangutan sidekick of the same name in Eastwood's Every Which Way But Loose comedy movie franchise.

However, Lewis is threatening to make a name for himself at the world titles after reversing his underwhelming heats form and sending a message by powering past Sun in the semis.

Remarkably Lewis, 21, only scraped into the 200m semis after qualifying 14th fastest for the 16-strong field.

Now Lewis is daring to dream of toppling 10-time world champion Sun in Tuesday's 200m final.

"It's big for me, but I have learned to compose myself over the last three years," Lewis said.

"So I will let the emotions die down because (Tuesday night), that's when it really counts."

Kyle Chalmers flounders

While there was ecstasy for Lewis, there was only agony for teammate Kyle Chalmers.

The Rio Olympic 100m freestyle champ failed to make the final cut, finishing a distant 13th in qualifying.

Chalmers is the Commonwealth 200m champion but he may yet ditch the event after his world titles disappointment, admitting he was weighing up the event ahead of the Tokyo Olympics.

Meanwhile, junior world champion Minna Atherton has emerged as another medal hope on day three of the world titles on Tuesday after qualifying second fastest for the 100m backstroke final behind Canada's Kylie Masse.

Former world champion Mitch Larkin is fifth fastest for Tuesday's men's 100m backstroke final.

Kiah Melverton and Maddy Gough will feature in a 1500m freestyle final expected to be dominated by United States' Olympic champion and record holder Katie Ledecky.