With the wave collapsing just behind him, this Man of Action beat the previous world record, set by Mike Parsons in Cortes Bay, California when he surfed a 77ft wave in 2008.
A native to Hawaii, McNamara was invited to Nazaré in Portugal for a big wave competition. There is an underwater canyon 1,000 ft deep, which causes some of the largest waves in the world.
There certainly is an element of danger, as the position of the canyon - which runs from the ocean to the coast - means that waves often break very close to shore.
What's extraordinary is that this was a spontaneous decision. Garrett had originally only agreed to tow a friend, Andre Cotton, out but as the waves grew bigger and bigger he decided to take it one step further.
'When we got round to the break it did seem big but I was just going to tow Andrew. But we still weren't expecting much. I didn't feel so good. Then the other guys were saying you've got to go. You've got to go and - boom! - I was on the rope and on a giant wave.'
But they say actions speak louder than words - so its worth going back and watching that again....