In front of thousands of spectators, the WSL's Tow Surfing Challenge comes to an abrupt end after one competitor suffers a serious injury. As the surfers process the news, they reflect on their tremendous love, fear, and awe of their unpredictable sport. Later, after sitting out the contest, Garrett puts his own injuries behind him and gets back in the water.

After the World Surf League announces that Nazare will host an upcoming big wave competition, athletes from around the globe arrive to participate in the tournament. But as the event grows in scope, so do Garrett's concerns over the proposed safety protocols. Later, the world-class surfers prepare for some of the largest, most unpredictable waves they've ever seen.

In 2017, prominent surfers flock to Nazaré for its largest swell to date and while one pro sets a new world record, Andrew Cotton suffers a devastating wipeout. In 2019, after rallying through a back-to-back concussion and broken foot, Garrett struggles with determining whether he's mentally ready to get back in the water.

A few days after his historic ride, Garrett is visited by his mother, whose presence prompts an exploration into his highly unconventional and turbulent childhood. In 2013, a group of Brazilians arrive in Nazaré, but their failure to heed Garrett's safety advice results in a near-fatal accident. In 2017, Garrett's appearance at a big wave competition takes a devasting turn.

In 2011, just as the largest swell of the season approaches, the McNamaras and their team reconvene in Nazaré, where they kick preparations into high gear to prepare for their upcoming attempt at making history. Then, despite some unexpected hurdles, Garrett catches a wave that forever changes him, the small seaside town, and the legacy of the sport.

After discovering Nazaré, Portugal's monstrous swells, pro surfer Garrett McNamara sets out to achieve his dream of riding a 100-foot wave.