The record-keeping agency is acknowledging a 44-year-old Hawaii pro surfer for catching a 78-foot wave off the coast of Portugal, saying the November run beats a 2008 record by more than 1 foot.
Big-wave surfer Garrett McNamara of Haleiwa, on Oahu's North Shore, told The Associated Press that the ride of his life was a fluke.
He said he originally didn't want to attempt the waves that day after wiping out numerous times on even bigger swells in the same spot, above an undersea canyon known as one of the biggest wave-generators on the planet.
"I was really beat-up that morning," he said. "This day, I did not want to get out of bed."
He changed his mind at the urging of friends, once they got into the ocean and he helped others catch a few waves.
"Everything came together," McNamara said Thursday. "Everything felt right."
Video of the run shows a minuscule 5-foot-10-inch McNamara against a wall of water as he lets go of a tow rope and begins riding down the wave at Praia do Norte. He briefly disappears into the break about 10 seconds into the run, then speeds up and remerges from the wave's tube as the swell quickly dissipates.
"I knew it was big, but I didn't know how big," he said.
McNamara said he didn't care at first about whether the wave was a record, but was urged by the townspeople in Nazare, Portugal, to get some kind of confirmation. He said he sent the footage and pictures to surfing legend and Billabong judge Sean Collins, who guessed the wave was 85 to 90 feet tall. Collins died in December.
The official record comes after McNamara was awarded $15,000 for the ride at the Billabong XXL Global Big Wave Awards in California last week.
Judges for the awards, considered the official arbiters of big-wave surfing, pored over footage and high-resolution still images from several angles to calculate a more accurate estimate, event director Bill Sharp told the AP.
They used McNamara's height in a crouch and the length of his shin bone to help compare it to the wave's top and bottom, Sharp said.
"You can't deny how big it was for that moment," Sharp said.
Sharp said surfers don't often get a chance to catch waves so big. He put the achievement on par with other infrequent athletic feats like four home runs in a game - which Texas Rangers outfielder Josh Hamilton achieved this week - or a perfect game.
"But add to that the fact that the stadium could collapse on you at any second," he said.
McNamara, who began surfing at age 11 and went pro at 17, said the achievement became more important to him when he realized it could help him urge more people to follow their passions.
"The world would be a much better place if everyone was doing what they wanted to do," he said.