Australia's water polo women have hailed their sharpshooting star Alice Williams as "a sniper" after her five goals inspired the Stingers to power into the semi-finals at the Olympics.

In an outstanding team performance at a packed La Defense arena, the 25-year-old left driver Williams provided the X factor for the Aussies with her jackal-like finishing in the 9-6 quarter-final triumph over Greece on Tuesday night.

Playing in front of the biggest crowd of their lives at Paris 2024's main swimming arena amid a rip-roaring atmosphere, the Stingers had to repel a stirring second-period fightback before taking control and setting up a mouth-watering semi-final against world champions USA on Thursday.

They're a win away from earning Australia's first women's water polo medal since 2012 and two from emulating the inaugural champions of Sydney 2000 - a sterling effort from a side hit by a COVID-19 outbreak at the start of this tournament.

"She's a bloody sniper," beamed Abby Andrews, enthusing about Brisbane's 25-year-old Williams, who's now netted 16 goals, plus three in shoot-outs, in the Stingers' unbeaten five-game trot.

Andrews, who also grabbed two goals herself while Bronte Halligan nabbed the other brace, added: "We're lucky to have Alice.

"We're a team of so many threats but to have her consistently show up and put balls in the back of the net when we need it most is massive. You can rely on her, she steps up in huge moments."

Australia were never headed after taking the lead in a cagey first period with Williams' first of two penalty strikes setting the tone.

Their only real concern for Bec Rippon's side came in a frantic two-minute, second-period spell when they saw a 3-0 lead evaporate in the space of two minutes as the Greeks rallied to level.

A lovely Andrews lob enabled them to reach halftime 4-3 up, but they were always in control after the break, with Williams deadly.

Andrews was thrilled the Stingers had put to rest the memory of their quarter-final losses in the last two Games.

"To lose by one in Tokyo was pretty devastating. This time around, we wanted to put the nail in the coffin early and stamp our authority. I think we did even though they caught up," she said.

"Defence has been our strength this whole tournament, and we showed that again."

It was a night of high emotion for the team, playing in front of a 15,000 sell-out.

"It was sick. Even at the anthem, I was a blubbering mess, couldn't keep the tears to myself," said Tilly Kearns, whose World Cup-winning Wallaby dad Phil and the rest of her family were in the stands cheering her on.

"As soon as that first whistle goes, it's just water polo like any other day - but a crowd like that just makes that victory a whole lot sweeter, makes all the hard work we've done over however many years really worth it."

A huge semi now awaits against global champs USA, who edged Hungary 5-4 in the later game. "Everyone knows they're a great defensive team, like us - maybe it might be a pretty boring game to watch, not many goals," Kearns said.

First, the men's Sharks will kick off an Australia-USA double when they taken on the Americans in the quarter-finals on Wednesday.