Stephanie Rice was out of contention and contemplating retirement while the expected gold from men's relay team bombed out because the Missile misfired on Day Two of fierce competition in London Olympics' aquatic centre.

But Australia's James Magnussen redeemed himself on Day Three, gradually pacing in the initial lap of the 100 metre freestyle semi-final round Tuesday night only to display a huge boost at the turn and slice the waters with ease and speed route to the last 50 metres.

"He swam a controlled first lap, turned in a good position and then brought in his famed back-end speed to burn off most of the field in the next 20 metre, before disposing of the last challengers to swim untroubled to the wall," News Ltd described Australia's most potent weapon in waters as he swam back to erase the embarrassing debacle suffered by the country on Sunday.

Two days ago, Mr Magnussen was a picture of dismal failure as his crew of 4X100 metre freestyle male tankers was shut out of the medal tally, disappointing their compatriots half-a-world away.

All eyes were focused on the country's foremost swimming hope for the gold but all he could offered was he became a victim of his inner belief that he was invincible.

"I came into these Olympics thinking I couldn't be beaten ... It was probably the reality check I needed," the Missile intimated in the ensuing news briefing after he competed in the penultimate 100 metre freestyle contest.

And he learned the painful way that the stress factor in London, or for that matter in any other Olympic Games, is all too different.

Mr Magnussen blamed his misplaced confidence and for not sleeping that much in the past 48 hours prior to plunging the waters on Sunday, which led to the Aussie warriors humbled by defeat.

The country's national anthem was not played and a shocked Australia wondered if Mr Magnussen will deliver the goods in the individual swim.

At the end of the 100 metre stretch, the man who touched the wall first and clocked the fastest qualifying time so far at 47.63 seconds was known to the world as James Magnussen, the same dejected man seen only two days earlier but a totally different athlete.

The fire inside blast him back to the winning lane anew and Mr Magnussen exclaimed afterwards: "It was a relief more than anything just to remember what it's like to go fast."

"It's so much easier when I'm going faster than when I'm struggling ... It felt really good tonight. It felt like I've still got plenty left in the tank. I'm happy," Fairfax reported the Aussie as saying on Wednesday.

Suddenly hopes went high again for the Magnussen believers and he affirmed too that "it would be great feeling if I could finish it off tomorrow night."

The likelihood is he would considering that Mr Magnussen swam faster than current record holder Cesar Cielho, who finished at 48.17 seconds.

The swimming star only needs to equal the best time he recorded in 2012 at 47.10 seconds to lay his hands on the gold medal.

And in time for the ultimate freestyle swim, the Olympian intimated that he was very focused to snatch what he failed to get last Sunday.

"I haven't read any media or done any social media and just concentrated on the win. I wanted it pretty bad," Mr Magnussen declared.

The only letdown seen last night was his compatriot, James Roberts, fell short of the cut when his speed of 48.57 only landed him to twelfth place.

Yet overall, Mr Magnussen characterised his remarkable feat as "a big confidence booster."