Relieved Australian surfer Taj Burrow has kept his world title dream alive by surviving fickle conditions and winning through to the Billabong Pro fourth round in Mundaka, Spain.

Burrow had to dig deep to compile 15 points to down compatriot Adrian Buchan (12.23) in conditions so bad that organisers postponed competition for the day immediately after their third round heat.

The West Australian scraped into the fourth round with fellow world title contenders Kelly Slater and Andy Irons.

Slater, 34, kept his goal of clinching yet another world title with victory at Mundaka on track but the crowd still left disappointed after he emerged with a tight 14.33 to 12.23 win over popular local hope Hodei Collazo.

The American superstar received a reality check when the crowds lining the river mouth in picturesque Basque country erupted as Collazo paddled out aiming to pull off a major boilover.

And the little known Collazo almost got his wish.

For a sobering moment Slater thought Collazo may have snatched victory on his final wave as the locals fanatically roared their approval - but it wasn't to be.

Three-time world champion Irons (11.76) was also counting his blessings after ousting Brazil's Yuri Sodre (10.60) thanks to his final wave.

Facing a major boilover, Irons pulled out a 6.43 point wave to scrape into a fourth round showdown with Australian Trent Munro.

Two other Australians won through to the fourth round on Wednesday.

Munro took out fellow Aussie Shaun Cansdell 13.73 to 12.96 to book a showdown with Irons while Phil MacDonald (10.33) held out compatriot Jake Paterson (4.67).

Australians Mick Lowe and Dean Morrison are yet to face off in their third round showdown.

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