Why Ariarne Titmus' retirement 'wasn't a shock' to Aussie swimming great Bronte Campbell

Australian swimming champion Bronte Campbell admits she isn't actually surprised by Ariarne Titmus' sudden retirement call.

The 25-year-old's decision to step away from swimming, effective immediately, stunned the world during the week, given the enormity of her success so far in her career.

She was one of the stars of the Paris Olympics and has four Olympic gold medals to her name.

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But speaking following the retirement call, Titmus admitted that she no longer had the burning passion for the sport to drive her to the 2028 games.

"My life has changed so drastically in the past 12 months, personally and professionally, outside the swimming," Titmus said.

"And I just lost the fire — totally lost the fire.

"I had a few challenges in the lead-up to Paris that really rocked me, and I guess I've been dealing with repercussions from that, and I have just put things into perspective and figured out what's most important to me.

"I don't think winning any more Olympic medals will change how I feel about myself and how proud I am of my career, and I just thought, 'I think it's time to move on from the next thing', and the time totally feels right."

Campbell, who won three Olympic gold medals in the pool herself, says long days and early mornings in the pool can quickly feel like burdens once you've lost that fire.

"It wasn't necessarily a shock to me," Campbell told Nine's Wide World of Sports.

"I've seen how much Arnie has had to give to the sport, and what's really important as you get older in the sport is the things that you're sacrificing end up being a bit weightier.

"When you're 17 and you're sacrificing going to the party down the road, it's hard, but it's not that hard.

"When you start to get a bit older and you're sacrificing your future career, Arnie has spoken a little bit about her health, you have to sacrifice everything for this single pursuit - that's what it takes to touch the wall first like Arnie has done for many, many years.

"Sometimes you just need to look up from the black line, look up at the rest of the world and be like, 'Wow, there're a lot more things out there', and maybe that sacrifice pile is too big and she's ready to move on with her life.

"The fire has to be there. If the passion is not there, the 4am wake-up is just really not worth it unless you're truly loving it. I think that's a special message anyway, chase the things you love and leave the sport while you still love it, rather than hold on, and your great memories end up being a little bit tainted.

"She's a really smart girl. She's made really clever decisions and taken the time to get it right."