Tyler Wright pumped her chest, thanked the ocean and set the scene for Sally Fitzgibbons as both stayed alive with late heat-winning waves at a cut-throat Margaret River Pro.

The women's Championship Tour field will be cut to 10 for the remaining five events, Wright entering in ninth and Fitzgibbons 15th, needing to reach the final four to guarantee safe passage for the first time in three years.

Wright is now safe and 33-year-old Fitzgibbons is now one win away after turning the tables on Caroline Marks in a tense round-of-16 clash.

The Australian scored a 7.50 inside the last three minutes to go ahead of the defending champion, holding on to win 13.10 to 11.57.

Fitzgibbons, who debuted on the top tour in 2009, was relegated in near identical circumstances by Marks a year ago and forced to requalify through the secondary tour.

"You have those heartbreakers; it hurts so much, takes so much to rebuild yourself," she said.

"Staring down the same situation and you walk back into it - that's the big win.

"No matter what happens I just want to fight to the end.

"You win the battle up here (in your head), and I heard the Tyler one too, it's inspiring to hear that."

In the previous heat, two-time world champion Wright produced a powerfully brilliant ride in the final minute to beat Tatiana Weston-Webb.

Needing a 7.80 to progress, Wright floated through the wash and found the rail on a tricky wave after competition had been moved to the nearby South Side break.

Wright clenched her fist and hammered her chest in delight then watched as the scores dropped, Wright's 7.83-point wave earning a 13.70 to 13.67 victory.

That ensured Wright will progress and instead left her Brazilian rival in danger of missing the cut.

"I haven't felt these kind of feelings ... in years," Wright said of the high-stakes nature of the mid-season cut.

"All thanks to the ocean on that one. I was just asking her, 'Hey I'm going to need your help here'.

"I'm fighting for my job right now and I love my job."

Only the five remaining women's round-of-16 heats were surfed on Thursday, with American Caitlin Simmers (16.43) easily accounting for Australia's Sophie McCulloch (12.33).

Fitzgibbons is now 12th on the live rankings while fellow Australian and quarter-finalist India Robinson is 14th.

Third-ranked Molly Picklum is the other Aussie through to the final eight, while four local men have progressed to the same stage.