Australian surfer Jamie Mitchell has trumped a field of experts to win the Portuguese leg of the World Surf League's big wave world tour.

Mitchell surfed three heats in punishing waves over 12 metres throughout the day to take the win and now moves to fifth position on the big wave world tour rankings.

"Today was next level, it was all about survival and it was heavy," Mitchell said of the break, Praia do Norte in the harbour town of Nazare.

"I saw all the guys take horrendous wipeouts. It was an incredible day and I'm sort of lost for words. I don't really know what to say."

The specialty event required a flotilla of emergency services to be on standby due to the size and volume of waves breaking throughout the event.

US surfer Damien Hobgood choosing to exit a wave in spectacular fashion ( Supplied: WSL/Masurel )

US surfer Damien Hobgood ejected over the back of a gigantic wave in spectacular fashion while fellow US surfer Nic Lamb had to be ferried back to shore after a nasty wipeout.

Mitchell, a former world champion paddle boarder, said the break offered unique challenges due to the unpredictability of the waves.

"It's not an easy wave by any stretch of the imagination," Mitchell previously told the ABC.

"But that's what makes it such a great wave. You never know what it'll serve up but you can be sure it'll be interesting, to put it mildly."

Gigantic waves pounded the iconic headland throughout the competition ( Supplied: WSL/Masurel )

Current big wave world tour ratings leader Grant Baker (ZAF) was eliminated in the earlier rounds but retains a solid lead on the ladder ahead of Brazilian surfer, Pedro Calado and Californian, Greg Long.

The tour now moves to Peru.