Mack Horton shocked at national 200m freestyle title win

Mack Horton Quinn Rooney/Getty Images

Perhaps Mack Horton summed it up best after winning a bizarre 200m freestyle final at the national swim titles in Brisbane on Monday night.

"What's going on?" the Rio Olympic 400m freestyle champion laughed.

Confusion reigned over who would represent Australia in the 200m freestyle at July's world titles in Budapest after Horton said he didn't want to do it and no one posted an individual qualifying mark in the final - including hot favourite Cameron McEvoy.

The three-time defending champion could only manage fifth behind shock lane eight winner Horton.

McEvoy looks set to miss an individual 200m spot but should still feature in Australia's 4x200m relay team in Hungary.

Olympic 100m gold medallist Kyle Chalmers was a surprise second in lane seven ahead of the unheralded Alexander Graham in third and rookie Jack Cartwright.

A top two finish under the qualifying time would have earned an automatic individual 200m world titles nod, with the top six then considered for the 4x200m relay squad.

But with Horton not keen to contest the 200m and Chalmers also a chance to pull out and concentrate on his pet event, the 100m, the jury is out on who will contest the four-lap event in July.

If Horton and Chalmers opt out, the two 200m individual spots look set to go to Graham - a 2013 world titles squad member - and 18-year-old rookie Cartwright.

Australian coach Jacco Verhaeren can technically use discretionary powers to slot McEvoy into the 200m field in Hungary with the sprint king already on the team after winning Sunday night's 50m final but is unlikely to do so.

In the meantime, Horton was among those scratching their heads over what the 200m final results actually meant.

Horton said he wasn't keen to contest the 200m at Hungary, preferring to focus instead on the 400m and 1,500m freestyle.

"I don't think so [contest 200m]. I would like to do it one day," Horton said.

"I was hoping to get onto the podium and secure a relay spot - I'll talk to Jacco."

In keeping with the odd 200m final, distance king Horton outgunned Chalmers in a final lap sprint finish to win as McEvoy faded.

McEvoy finished more than two seconds outside his 200m personal best time.

"I don't know what is going on to be honest - it's a bit of a surprise," Horton said.

"I haven't done any 200m work. I literally just rocked up and had a crack."

Chalmers also entered the 200m event "for fun", hoping to simply make the final.

He is expected to dominate Wednesday night's 100m final.

Other Monday night winners were four-time Olympic medallist Emma McKeon (100m butterfly), dual world champion Emily Seebohm (100m backstroke), Taylor McKeown (100m breaststroke), Blair Evans (400m IM), Matthew Wilson (200m breaststroke) and Brayden McCarthy (50m butterfly).