‘What we found was super special’: inside the quest for the 100ft wave

A new six-part documentary series follows the community of big-wave surfers at Praia do Norte in Nazare, Portugal, and hunt for ocean's Everest

It started as a picture. In 2005, Dino Casimiro, a sports teacher in the fishing village of Nazare, Portugal, snapped a photo of what he had long observed from the seaside cliffs: swells in the Atlantic the size of buildings, so feared and unpredictable it seemed everyone in town knew of someone who had been lost at sea. The image was stark, magnetic - a wave that appears at level with the cliff, the whitewater break like a cumulus cloud. I immediately thought that I need to do something," he recalls in 100 Foot Wave, a new documentary series for HBO. So Casimiro emailed the photo to American surfer Garrett McNamara with a simple question: could you come see if my wave is that big?

McNamara, 53, would know; a pioneer of big-wave surfing, in which jet skis tow a surfer in and out of pounding swells, he had pushed the boundaries of what's considered surf-able throughout the 2000s. He'd won the Tow Surfing World Cup in Maui in 2002, traveled from California to Tahiti, surfed the tsunami of a calving glacier in Alaska. And he was looking for what seemed an unfathomable prize: a 100ft wave, the ocean's Everest, potentially possible under fluke conditions at a few spots in the world. In 2010, five years after Casimiro's offer, McNamara and his now wife and manager, Nicole, went straight from the airport to the Nazare's 17th-century lighthouse, long abandoned. It was stormy, so windy the crew could barely open their car doors. When we pulled up and saw the waves," Nicole told the Guardian, Garrett just looked at the kid" - a videographer sent by the town's city hall - and said Do not turn off the camera.' And every day it was just a constant reminder of Film this, film this, film this - because we knew what we found was super special."