Following a massive win at a competition at Maui's world-famous Jaws surf break in 2003, professional surfer Garrett McNamara comes out of retirement to pursue his lifelong dream of riding a 100-foot wave. In 2010, Garrett and his wife Nicole invite fellow big wave surfers to Nazare, Portugal, where the monstrous, untapped waves just might help McNamara achieve the impossible.

In 2011, just as the largest swell of the season approaches, the McNamaras and their team reconvene in Nazare, 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.

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 Nazare, 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 devastating turn.

In 2017, prominent surfers flock to Nazare 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.

As the world's top surfers arrive in Nazaré for the WSL’s Tow Surfing Challenge, Garrett grows concerned over proposed safety measures.​

After the WSL competition abruptly ends, the athletes reflect on their beloved, unpredictable sport. Later, Garrett attempts to surf again.