Australia will again have three surfers challenging for a world title with Ethan Ewing joining Jack Robinson and Molly Picklum at the California one-day decider next month.

Robinson and Picklum already secured their top-five rankings with early success at the Fiji Pro before Ewing's passage to the final four meant last year's runner-up also punched his return ticket.

The World Surf League's top-five men and women will compete in a one-day, winner-take-all contest at Lower Trestles in California next month.

Fifth surfs against fourth in a knockout heat for the right to face the number three, the field whittling down before a best-of-three heat equation against the number one seed to decide the title.

Ranked fifth entering the event at Cloudbreak, Ewing moved up to number four thanks to his victory on Saturday morning over Hawaii's Barron Mamiya and Robinson's elimination of his closest rival, Brazil's Yago Dora.

The 25-year-old Queenslander finished runner-up to Brazil's Filipe Toledo for the world title last year, defying multiple fractures of his vertebrae suffered barely a month earlier to surge within reach of a remarkable maiden title.

"It feels amazing (to lock in a spot in the Finals) — this year has been a lot of ups and downs and I felt like, towards the end, I was just holding on,'" he said.

"I made a lot of mistakes in a few of the comps so it feels good to secure that and get another chance at a world title."

Olympic silver medallist Robinson had a tighter battle with the in-form Dora before securing his quarter-final triumph 12.33 to 11.60.

But neither Australian was able to progress to the decider, Ewing's (15.17) early nine-point ride not enough in a high-scoring loss to Indonesia's Rio Waida (16.26).

Robinson lost to second-ranked Griffin Colapinto, who then beat Waida in the final.

Picklum and compatriot Tyler Wright also lost their semi-finals at Cloudbreak on Saturday, the women's event won by the Kelly Slater-coached teenage wildcard Erin Brooks in her Championship Tour debut.

Already boasting the scalps of Gabriela Bryan and world number one Caitlin Simmers, the Canadian 17-year-old led from start to finish to oust Picklum, 15.26 to 11.80.

Wright was beaten by Tatiana Weston-Webb, the Brazilian sneaking into fifth as a result.

Brooks didn't blink in the final, finding two seven-plus point waves in an emphatic introduction to the big time.

Cloudbreak was back on the tour after a seven-year absence and will replace Lower Trestles as the finals destination in 2025.

AAP