It was the Aussie teens' fourth consecutive victory in their unbeaten campaign, but South Africa's own attack made them work harder than at any time so far in the tournament in the first Super Six-stage match in Windhoek on Sunday.
Queenslander Charles Lachmund was the quickest and the best of Australia's hostile and accurate pace unit, taking 3-29 as South Africa were skittled for just 118 off 32.1 overs after being inserted by captain Ollie Peake.
But player-of-the-match Lachmund was given ample support by the rest of the quartet who've been dubbed the 'fearsome foursome' as Will Byrom took 2-16, Hayden Schiller 1-10 and Kasey Barton 1-34 with Australia now already looking nailed on for the semi-finals.
Aryan Sharma ensured the quicks didn't completely hog the show, the left-arm spinner chipping in with 2-27 as all five bowlers celebrated a wicket.
But the victory didn't come easily, with the Aussies, who had won their first three matches in chases without losing more than two wickets, this time having to work hard to subdue a lively South African attack, who got rid of star left-hand opener Will Malajczuk in the third over, courtesy of a dazzling catch by Armaan Manack.
Nitesh Samuel, the bolter selection who's impressed with his steadying knocks throughout the event, was finally dismissed for the first time, caught for 16. It means his average for the tournament is now 172 after his four innings.
Captain Peake, who'd been impressing in the BBL before the World Cup, missed out for 10, caught behind off a wild cut, but Steven Hogan, a centurion in the opening match against Ireland, again displayed a calm head and impressive technique with 43 off 73 balls.
Once he became the impressive JJ Basson's third victim with Australia four down and 25 still needed, keeper Alex Lee Young and Jayden Draper, both unbeaten with scores of 21, survived a few more alarms to guide them home on 4-122 in the 33rd over.
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