And what a ride it's been.

The 28-year-old finally decided to hang up his swimming cap on Wednesday, bringing to an end a career where he achieved almost everything the sport had to offer.

While he fell short of an Olympic gold medal, Magnussen admitted he had no regrets in a decade-long stint at the top of world swimming.

"It's been a crazy ride and I can never be accused of having a dull career, but I've enjoyed all of it," he said.

"I'm not the person that lives with regrets ever, regardless of whether I've made mistakes or not, I've always learned from them."

Ultimately, the realisation that his best days were behind him was the deciding factor that ended his quest for a spot in the Australian swimming team at Tokyo next year.

"The big thing for me was if I was going to Tokyo I wanted to be somewhere near my best and felt at this point in my career I couldn't be," he said.

"I've been to two Olympic Games, so I know what they're all about and it's not as exciting as a prospect as when I was younger."

"There was no point pushing it any longer if I was going to be underdone and I'm not swimming as fast now as I was a few years ago."

Magnussen was confident that while he could have gone to Tokyo and earned a spot in the men's relay team and the 50-metre freestyle, he wanted to go there aiming to win.

"I set myself pretty lofty standards throughout my career, had very high expectations and didn't think I could maintain that high standard going into Tokyo," he admitted.

The two-time world champion said he thought as a youngster the Gold Coast Commonwealth Games would potentially be his last event.

It turned out to be the case.

"When I sat back and weighed up what I'd have to sacrifice to go around again for another Olympic Games, I was content with everything I'd achieved and was ready to move on," he said.

"I took plenty of time to make the decision; I didn't want to rush it because I didn't want to second-guess myself and talk about a comeback.

"It wasn't like I couldn't do it anymore because my body can't, it's because I'm going out on my own terms."

The Port Macquarie product said he would never have envisaged as a 17-year-old what he was able to experience and achieve in the pool.

"If I could speak to 17-year-old James, I'd just say to enjoy it and don't take yourself too seriously because at the end of the day it's just sport," he said.

Now, Magnussen has a few business pursuits he is working on and indicated he would like to give back to the Port Macquarie community that gave him so much.

Don't rule out seeing him at Town Beach sooner rather than later.

"Having such a good upbringing and having such a great support base around me in Port Macquarie was a big part of my success," Magnussen said.

"Hopefully some time in the future there can be some business pursuits back up that way where I can give back to the community."