WA's Bronte Macaulay has continued her dream run at the Margaret River Pro by the barest of margins, while seven-time world champion Stephanie Gilmore came up trumps against Sally Fitzgibbons.
Macaulay and Frenchwoman Johanne Defay finished in a tie during their quarter-final showdown on Thursday, with both surfers posting a two-wave total of 11.83.
But it was Macaulay who walked away with the win because her highest-scoring wave (6.83) was better than Defay's (6.50).
Macaulay has never reached a WSL final, but the Gracetown local will have the chance to do that when she takes on Brazilian Tatiana Weston-Webb in the semi-finals.
"I'm so thrilled to make it into the semi-finals," Macaulay said.
"That was a hectic heat, especially at the end. The rain was making it hard to see my line-ups and it was even hard to see where Johanne was after she got that last wave and if it was good.
"I didn't know what was going on, so it was super stressful. I'm so stoked to make it, it's really special, especially at home.
"All of my family have been coming down each day and cheering me on, so it feels good to keep making heats."
Gilmore pulled off a near-perfect 9.5 ride during her heat to edge Fitzgibbons 15.73 to 14.17 and book a semi-final berth against four-time world champion Carissa Moore.
"It was a good battle with Sally, we've had a lot over our careers," Gilmore said.
"It feels really good to break the quarters. I haven't done that this year. I feel like this whole event I haven't had an opportunity to hit the lip, so it was nice to get that great wave."
Australian Tyler Wright fell to Weston-Webb, while Isabella Nichols was eliminated by Moore.
In the men's competition, world No. 1 Gabriel Medina, world No. 4 Kanoa Igarashi, and Australian Olympic qualifier Julian Wilson were all eliminated in the round of 16.
Hawaiian Seth Moniz caused the upset of the day when he pipped Medina 9.84 to 9.53.
"He got me in a semi-final at Teahupo'o and it hurt, so it felt good to get one back on him," Moniz said.
Wilson was bundled out by Jordy Smith, while Igarashi was defeated by Matthew McGillivray after copping a penalty for interference.
Ryan Callinan is the only Australian who made it to the quarter-finals after beating Frederico Morais.
John John Florence, Griffin Colapinto, Italo Ferreira, and Filipe Toledo also made it through to the final eight.