Tyler Wright, Ethan Ewing and Ryan Callinan are flying the flag for Australia after a day of upsets at the World Surf League's Rio Pro at Saquarema's Praia de Itauna.
World No.2 Wright earned her sixth semi-final appearance of the season and will take on young American Caroline Marks, who won at the last tour stop in El Salvador.
Wright overcame Hawaiian Gabriela Bryan, posting an impressive score of 7.83 on her second wave to set up the quarter-final win.
"You have to use a lot of flexibility in your mindset to know that it's not going to go as planned out there," said two-time world champion Wright.
"In that heat, there were multiple unexpected things for me.
"It's about adaptability here in Brazil and knowing it's going to be a lot of work."
Fellow Australian Molly Picklum (10.30) fell to another youngster, American Caitlin Simmers (11.40) in an exciting showdown.
Current World No. 1 Carissa Moore became the first surfer to clinch a spot in the WSL Finals, and will take on Simmers in the semis.
"We have two events left after this so it obviously takes a little pressure off and I'm super stoked," said Moore.
The top three ranked men - world No.1 American Griffin Colapinto, four-time Rio champion Filipe Toledo and fellow Brazilian Joao were all eliminated, leaving Ewing as the highest-ranked surfer in the quarter-finals.
Injury replacement and former CT surfer Brazil's Jadson Andre took out both Colapinto and Toledo, who required medical attention after falling on his last wave attempt.
With No.5 Gabriel Medina also a casualty, Australia's Jack Robinson missed a chance to leap-frog him in the rankings when he was brutally penalised for a non-priority interference which meant his second counting wave was zeroed.
Despite securing a wave in the last seconds he fell to Seth Moniz in the elimination round, but Ewing got some revenge for his countryman when he ousted the Hawaiian in the round of 16.
He will next take on Italian Leo Fioravanti in the quarter-finals.
Callinan progressed to a final eight match-up with Brazilian wildcard Samuel Pupo by beating Japan's Kanoa Igarashi in a tight battle.
Queenslander Liam O'Brien went down in his round-of-16 clash with another local hope Yago Dora.
The titles will be decided Saturday local time.
