Gymnasts on narrow beams, helmeted kids skimming in skate parks — those are hazardous pursuits, sure. But at least the wood and concrete don’t rise up and chase you, seeking to slam you down on razor reef teeming with life and rake you over it like a meat slicer. Going into the final rounds, Teahupo’o already had injured two surfers, and that was in small conditions, with a larger swell scheduled to build. Australian Jack Robinson took five stitches in his foot merely in training. The injury didn’t prevent Robinson from eliminating American John John Florence in a heavyweight Round 3 heat amid building surf that inflicted early wipeouts on both. Frenchwoman Johanne Defay suffered a head wound in a heat Saturday that required four stitches.

“It’s a cheese grater,” legendary big wave surfer Laird Hamilton said by phone from his home in Malibu, Calif. “You fall, you’re going to shred yourself.”

Be sure of this: If larger waves do come in for the quarterfinals, a lot of surfers will fall. “If it’s severe, it’s going to take out most of the field,” Hamilton predicted.

Teahupo’o is the most philosophically interesting competition at the Paris Games, and not just for the question of whether it’s right to impose a judge’s tower on surfing or to build it on a shimmering coral reef. The place seems sacred. There is something about the teeming energy in that wave that resolves into such a smooth glassy cylinder. It restores the sense of power to that word, sacred, reminds you that it means something about true dominion.

“It’s the most perfect wave in the world and the most frightening and wicked in the world,” Morocco’s Ramzi Boukhiam has said. “She has two faces. You see it from the outside, you look at it from the boat, you’re like, ‘Wow, it’s magnificent.’ But when you’re inside, you fall, poof, it’s less magnificent.”

Back in 2000, Hamilton stunned the world by catching a ride at Teahupo’o that is now known as the “Millennium Wave.” A photo on the cover of Surfer magazine captured it, a murderous ledge of water hanging over Hamilton’s head with the caption, “oh my god …” The photo effectively opened Teahupo’o, formerly ridden only by a handful of locals and elite pros, to the world. “It changed people’s perspective of what’s rideable,” Hamilton said. The sensation of all that green-blue majestic energy was so profound that afterward, Hamilton wept.

“It’s not so much the vastness of the wave,” Hamilton told me a few years ago about why he chases such seemingly unrideable masses. “It’s more about the insignificance of us. When you become insignificant is when you truly begin to participate. That’s when it becomes a harmonious act.”

Peruvian surfer Sol Aguirre had a similar reaction when she took off on a wave in training. Initially she felt fear, but then it resolved into that beautiful translucent tunnel and a cloud of white spray. “I started crying because it was a really beautiful ride, and I managed to make it through,” she said, according to the official website of the Games. “You make it out, and it’s like: ‘I’m alive. I’m living it.’”

A harmonious act. That’s what Teahupo’o really requires to bless riders. There’s no making the wave submit. Water is 800 times denser than air. Saltwater weighs 64 pounds per cubic foot. Combine that heaviness with the peculiar oceanography of Teahupo’o, and it creates a unique hydraulic problem: The wave is a cylinder of centrifugal reversion. It sucks water from the base of the shoals steeply and powerfully up its face — and will take you with it. Choose a line too high, and the backspin of the water will grab your board and gyrate you up and over the falls. Even a small whack from that heavy lip can do a certain amount of damage: A year ago during a training camp, New Zealander Saffi Vette got a little forward on her board, and the lip broke right on the back of her leg. The blow was so heavy it tore her medial collateral ligament.

But if you survive the initial plunge — the suck, the angle, the velocity — it’s heavenly. “That wave, because of how quickly it rises up, you have to get in early and get yourself set to take the drop, the descent, and then pull up into it,” Hamilton said. “It’s all about the start. If you got a good start, then you’ve got a good chance, and it can lead to a more dramatic ride. If somebody is doing it correctly, there will be an ease to it that is deceptive for the difficulty.”

Ease, harmony — that’s what the competitors seem to feel when they catch the break right. The best ones, those who medal, will exhibit a sense of collaboration with all that effervescence. If Teahupo’o gets large, watch the Tahitians in the round of 16, Kauli Vaast on the men’s side and Vahiné Fierro on the women’s. They are most familiar with it, have a regular acquaintance with the outermost brink of things there.

Why does Teahupo’o provoke such powerful emotions from surfers? Perhaps it’s partly a physical response, a release from tension. Surfing is an experience of full body intensities. The transfer of all that metabolic high energy excites neuronal signals. We’re all creatures of light and electricity as well as tissue — inside us is a swarm of fireflies. The triggered chemical-emotional reactions that come with stress produce a heightened clarity, an “alertness” Hamilton said, “and we’re meant to experience that.”

Teahupo’o is a challenge, even on its easiest day. There is no beating it. You don’t defeat the ocean coming home to those cliffs. You just cooperate with it — until it lets you go.