Teenager Sienna Toohey shines at the Australian Swimming Trials with 100m breaststroke final win

Australian swimming has a new young star: Sienna Toohey.

The 16-year-old booked her ticket to the World Championships in Singapore next month by beating Australia's best women in the 100m breaststroke final at the Australian Swimming Trials in Adelaide.

Her time of 1:06.55 smashed her personal best.

Toohey broke down immediately after the race in an interview.

"I was just so nervous, but I'm just so happy that I've done it now," she said.

"It's a lot.

"I've been doing very hard training — more than I've ever done before so I'm very happy that it's paid off."

Toohey said she had the toughest week of training in her life earlier in the year with the national squad.

"It (winning) was definitely a relief if anything because spending time away from family for that long, it's the hardest it's ever been for me," she said.

"Because I love my dad and my brother so much, it was very hard not having them while I was doing that tough training."

The upside was training alongside her idols.

"These were people I was watching two years ago saying I want to be just like them, so it was very surreal being in a hotel room with them, eating lunch and dinner," she said.

In April, Toohey broke breaststroke legend Leisel Jones's record for 16-year-old girls.

"After nationals this year, she sent me a video the night after I broke her 100 record, just congratulating me," she said.

"It meant a lot. Just getting something personalised from her. And her just reaching out and telling me to keep going and that things can happen when you're a young age. It was definitely inspiring."

Toohey said she only started swimming because she wanted to play water polo.

"But my parents told me I couldn't do water polo if I didn't swim," she said.

"It got to the point where I had to choose swimming or water polo, obviously I chose swimming, it was the right choice."

In second place was Ella Ramsay who will add the 100m to her Singapore dance card after already qualifying for the 200m individual medley on the first night of the trials.

She was asked what advice she has for Toohey.

"To keep following your dreams I'd say," Ramsay said.

"Just to see the pure emotion and relief Sienna had after her race, I definitely can relate to that because I had that this time last year when I made the Olympic team."

Meanwhile, multiple Olympic champion Kaylee McKeown is winning, but struggling.

After she was disqualified, then reinstated, on day one of the trials, she followed up with a win in the 100m backstroke, but said she was far from happy.

"Yesterday was yesterday, today is today, can't really dwell on the past, that's the sport," she said.

"This week's just not my week, but I've gotta do my job and make my team."

She said she wasn't satisfied with her winning time of 57.71 — 0.38seconds outside her personal best which was the previous world record.

Even so, it's the third fastest time of the year, behind her own win in the national championships earlier in April, and world record holder, Regan Smith in May.

"I mean it's pretty simple you want to swim fast," she said.

"You just want to go out hard and come back hard and hope for a good time on the wall and it just wasn't there tonight."

On Monday, Alexandria Perkins won the women's 100m butterfly final and on Tuesday she beat her own personal best in the heats of the women's 50m butterfly in the morning, setting an all comers record before beating it again, winning the night's final.

"I feel like I've held myself to a really high standard and I know the way I train so I can take confidence from that," she said.

"I feel like it's maybe taken a few years to translate the way I'm training to the way I'm racing. So, I'm finally feeling I'm achieving that.

"It's very exciting, it's also scary because you don't know when it's going to stop.

"You can't put a limit on it, you never really know."

In Singapore, she will come up against US 100m butterfly world record holder, Gretchen Walsh, after coming third against her in the 50m and 100m butterfly finals at the World Short Course Championships in Budapest last year.

"You don't want to be next to her because you can get stuck in her wash a bit because she's just so damned fast," she said.

"But I think it's incredible what she's doing for the sport, but hopefully she'll drag all the flyers along with her."

Paralympic star Alexa Leary blitzed her field, coming within .01 seconds of her world record in the S950m freestyle final, but said she was glad she didn't break it.

"The big show and the big game is Singapore. For this one I was just really focused on what my coach was focused on with all my skills and drills," she said.

"I'm strong in the mental game so I've got this in Singapore, I've got it."

In other results, Edward Sommerville smashed his personal best by over two-and-a-half seconds winning the men's 200m freestyle final in a time of 1:44.93 — comfortably under the World Championships qualifying time.

Sam Short came second to back up his win in the 400m on night one.

Olympic veteran Matthew Temple won the men's 100m butterfly final to qualify for Singapore alongside Jesse Coleman in second place.