Australians Jack Robinson, Liam O'Brien and Ryan Callinan are quarter-finalists at Sunset Beach, but leading Aussie surfer Ethan Ewing has crashed out of the Hawaii contest.
Ranked world No.2 heading into the season, Ewing took down 11-time world champion Kelly Slater early on Sunday, with the surfers battling wild three-metre waves and windy conditions on Oahu's North Shore.
But the 25-year-old struggled for high-scoring waves in his round-of-16 clash with fellow Queenslander O'Brien, outpointed 13.83 to 7.67 for their best two waves.
"The ocean felt like it was working with me a bit," said O'Brien, who was ousted by Ewing at the same point in the season-opening Pipe Pro.
"I've had so many heats where I've just been lost at sea, so it's nice to get one where I get a couple of waves.
"Obviously that was always going to be a really hard heat, Ethan's just so good out here, so I'm really happy to get past that one and we'll see how we go in the next."
The 24-year-old set up a quarter-final match-up with Callinan, with the Newcastle surfer getting the better of Sydneysider Connor O'Leary, who now surfs under the Japan flag.
Robinson, who ended last year ranked No.5, bested in-form American Jake Marshall 14.66 to 11.77 and will now face Brazilian ace Italo Ferreira.
With difficult wave selection behind a number of upsets through the day, the rankings are set for a shuffle, with two-time world champion, Hawaiian John John Florence, in the hot seat to take over the leader's yellow jersey.
A runner-up at the Pipe Pro, Florence can claim top spot after the early exit of his compatriot Barron Mamiya.
Relishing the unruly conditions, Florence posted the best two-wave score of the day, 16.06, en route to a quarter-final clash with South African veteran Jordy Smith.
"It feels really good to just be chipping away at heats - I'm really enjoying it and the challenges that every heat brings and trying to just be OK with that and not be too hard on myself," said the 31-year-old, who won world titles in 2016 and 2017.
Others into the final eight include another Hawaiian, Seth Moniz, who will face Japan's Kanoa Igarashi.
Because of the North Shore permit rules over a Hawaiian public holiday, the next possible day of competition is Wednesday (AEDT), with the women's field still to take to the water.
