CANBERRA, March 1 (Xinhua) -- One of the most anticipated freestyle races in Australian history has lived up to expectations on the opening day of the Australian Swimming Trials.

Kyle Chalmers, the 100 meter freestyle gold medallist at the Rio 2016 Olympic Games, upset fellow Rio gold medallist Mack Horton to win the 200 meter freestyle with a time of 1:46.49 on Wednesday night, just 0.27 seconds quicker than Horton.

"Honestly, it is the best feeling I've had in quite a while, it has been a hard 12 months. To get back racing on the national stage, and to get my first long-course title, means so much to me," Chalmers told reporters.

Earlier on Wednesday, 22-year-old Gold Coast local Alexander Graham raised eyebrows when he swam a personal best time to qualify fastest for the 200 meter final, eventually finishing third to his Olympic champion teammates.

Two-time Olympian Cameron McEvoy put in a disappointing performance, completing the final in a time of 1:48.67, more than three seconds slower than his personal best and a second slower than his qualifying time.

The trials, running at the Gold Coast Aquatic Centre until Saturday, represents the final opportunity for members of the swimming team to qualify for the 2018 Commonwealth Games, also to be held on the Gold Coast.

Ariarne Titmus, 17, was one of the bright sparks of the first day, swimming a personal best time in the 200 metre freestyle to qualify.

The 200 meters was the first of three events for Titmus who will swim in the 400 meters on Thursday and 800 meters on Friday.

"It's exciting, I've got a lot more speed now and it means I can go out harder and it won't hurt as much so that's a good thing," she said.

Two-time world champion Mitch Larkin, 24, qualified for the 100 meter backstroke at the games with a time of 53.57; a significant turnaround in form after struggling for much of 2017 after changing coaches.

"The plan is to really find my groove and to build my strength from there. Tonight was a really good swim. I'd like to go quicker and I know I can," Larkin said.

Two-time Olympic medallist Emily Seebohm also qualified in the backstroke; the third time she has made the Commonwealth Games team.

Despite forfeiting the 200-meter crown to Chalmers, Mack Horton said that main focus for the event was qualifying for the 4x200 meter freestyle; a feat he accomplished with his second place finish.

"I got what I needed out of it," Horton said.

"I love that relay, it's good fun, one of my highlights from Rio was the relay, it is probably as good as the gold medal, it is a fun event to be a part of and I want to do that."