A Hawaiian surfer may have beaten his own world record for riding the largest wave ever surfed - a monster 30-metre wall of water off the coast of Portugal.

If the claims are verified, big wave surfer Garrett McNamara will go into the Guinness World Records with his incredible ride on a wave estimated to be more than six metres higher than his previous record, set at the same spot at Nazare in Portugal last year.

Photographs and video taken on January 28 show the 45-year-old as a small speck on a towering wave as he plunges down its face. He rides numerous sets, at one stage wiping out on the face of a wave and diving into the churning water.

McNamara was towed by a jetski onto the largest wave, which formed over an undersea canyon known as one of the biggest wave-generators on the planet.