A big storm was barrelling east across the Pacific Ocean in late December 2024. Alo Slebir couldn’t sleep while flying through its turbulence on his way back from Maui home to Santa Cruz. Big winter storms in the North Pacific send big waves to Mavericks, a surf mecca just north of Half Moon Bay, and big waves are what Slebir lives for. Each year, between September and April, a handful of opportunities arrive to ride energy of this magnitude. Slebir had been obsessively watching the swell charts. “This could be it,” he thought.
“Big” waves start at around 20 feet, in the highly subjective calculus of the surfing world, but at Mavericks they can get way bigger. Sometimes they get so big and fast that surfers can’t paddle fast enough to catch up on their own, so a partner on a jet ski whips them from a tow rope into the wave. On December 23, Luca Padua and Slebir, both then 23, were trading off driving the jetski and holding the tow rope. They had been out all day on coffee and no breakfast when the big one showed up that afternoon. The waves marched in unusually long intervals, one every 25 seconds or so, which gave them more time to grow in size. Some waves, Slebir says, you can gauge the size just from the sound. This one was a roar. It was Slebir’s turn on the rope when he saw it. “A giant wall of water from Moss Beach to Half Moon Bay.” It formed a perfect scoop like the bowl of a skateboarder’s half-pipe.
Padua throttled up to the ski’s max speed of 55 miles per hour; Slebir’s board had special weights to keep it from lifting off the surface at that speed. As precisely as a quarterback throws a winning touch down to his receiver, Padua placed Slebir at the top lip of the scoop. Slebir didn’t keep the tow rope taut to get extra speed, as he sometimes does, because he knew this huge a wave would generate more speed than most as it dropped out from under him. Captain Marc Alley, watching from a boat, saw the biggest wave he’d seen in 35 years: “The rope was totally vertical, hanging straight down,” he says. “He’s not behind the jetski. He’s directly under it.”
Slebir cannot provide a play by play, exactly. He remembers the speed and the never-ending drop, and how time stood still. “You kind of black out,” he says. “You’re so focused on doing that one thing, you don’t have time for memory.” Photographers and videographers captured the forty interminable seconds. Sky and sea were dark and gray. A huge black maw behind a roaring white wall seemed to chase a tiny Slebir as he carved a perfect line down the face. A few days later, Pacifica-based photographer Frank Quirarte reckoned, on Instagram, that the wave was 108 feet tall—breaking a long-sought 100-foot benchmark.
But after the surfers and the cameras had moved on, the broken wave kept going—if now with an attenuated power—and ended its journey by crashing into the black rocks at Pillar Point. There it met a motley assemblage of intertidal characters: squat limpets and lithe, frondy sea palms; leathery sponges and squishy nudibranchs. Hard or soft, they all evolved to thrive, like Slebir, amid the enormous waves at their doorstep. What does a big wave matter to a nudibranch, a starfish, a mussel? How can they survive it? “We can be awed by imagining the physical brutality of life on those rocks,” writes Mimi Koehl, a longtime U.C. Berkeley marine biology professor and tidepool expert, in the book Wave-Swept Shore: The Rigors of Life on a Rocky Coast. “Are we right?”
In the days and months after Slebir’s ride, a surfing-world circus began swirling around the wave, poring over fine points of the photographs, video, and weather data. All were united by an urge to grasp an ephemeral thing. It was, of course, just one wave among an uncountable many that have been hurtling toward Pillar Point for millions of years, shaping the shoreline and the life that clings to it.
If you really want to get your head around a Mavericks wave—how it became such a behemoth, and what it means to the living things that encounter it—you have to start with the rocks.
The tectonic birth of a big wave
Most of the year, waves come at Pillar Point from the northwest, hit the gentle slopes northwest of Sail Rock and peter out, never getting big enough to write home about. But in the winter, waves arrive from the west-northwest that have been born in the “wave factory” of intense storms in the Gulf of Alaska or off the coast of Japan. Some waves have long periods—the time between each crest—which lets them build speed and size. This alone is not enough. The breaks at Mavericks owe their particular, bodacious character—that clean slab, the towering scale—to plate tectonics, says Ryan Seelbach, a geologist and big-wave surfer.
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The key moment was sometime in the Pliocene epoch, between 5.3 and 2.6 million years ago, a time when giant herbivorous sea cows roamed California’s coastline. Two plates crashed together and created the San Gregorio Fault. Their collision crumpled, twisted, and uplifted the shallow bedrock, creating a place—a shallow bowl—where the seafloor goes abruptly from 100 feet deep to 20 feet deep, near Pillar Point. When a swell reaches the bowl at the right angle, it slows and jumps immediately. It has nowhere to go but up. It stacks up—leaps up, really—doubling in size, says Mark Sponsler, who started the StormSurf wave prediction website in 1996. Then it crashes, sometimes forming not only a half- pipe bowl for the surfer to drop into, but a full pipe or cylinder of water—the holy grail known by surfers as a barrel. Bowl or barrel, the wave can be ridden a full half-mile, an extraordinarily long journey for a surfer who is up to the challenge.
The dark side of this geology is that occasionally, a surfer who wipes out is sucked off the wave and drilled by its force into much deeper water. Sometimes surfers encounter a terrifying part of the rock bottom known as the “underwater waterfall.” Kyle Marty, a Santa Cruz surfer, says, “It’s like jumping off a skyscraper.”
There is one more ingredient in the recipe for the biggest of waves—a phenomenon one of us may have witnessed. Sachi, who is a surf photographer, was out at Mavericks that day in December with her camera, and was waiting on shore for a ride out when the wave of the day rolled through. Just before Slebir’s wave, she saw the edge of the sea do something strange: it retreated several feet from the shoreline. It may have been a sign of another, sneakier wave than the big ones everyone was watching, according to Tuba Özkan-Haller, a physics professor who studies waves at Oregon State University.
Physicists call the wave sets that people surf “gravity waves,” because gravity is what eventually settles them down. But underlying these, stretching across a set, are longer waves that never break, called “infragravity waves.” Özkan-Haller has studied how they contribute to sneaker waves—those waves that occasionally rush up a beach much farther than all the others and sometimes take lives. Out in the surf zone, the trough of the infragravity wave lowers the water depth, which enhances the height of any simultaneous gravity wave. Thus a monster is born. “They say you’re riding waves,” Sponsler says. “But what you’re really riding is pure energy.”
OK, if you care about size …
The native Hawai’ians who introduced surfing to California usually measure waves from the back side, not down the face. That didn’t sit right with Bill Sharp, a former Surfing Magazine editor who visited the North Shore of Oahu throughout the 1980s: “The waves would be clearly 25 feet when they’re landing on your head and people would go, ‘Oh yeah, 8–10 feet.’ It just drove me nuts.” Sharp came up with the 100-foot benchmark as a “marketing hook” to get funding for surf competitions, likening it to running a four-minute mile. It caught on.
Surfers have dabbled in all sorts of measurement technologies. Grant Washburn, a filmmaker who has surfed Mavericks more than any human on the planet, dropped a buoy from an airplane in 2023 into the wave zone to gather real-time data about the swell’s angle and timing. He wasn’t just interested in size; he wanted to figure out details like why surfers drifted to the north before a giant set came, and to predict future waves with more accuracy. He’s also worked on plans that involved filming a surfer wearing a wetsuit with ruler-marks on it, and driving a boat covered in instruments in front of a breaking wave. The car company Porsche has teamed up with a German big-wave surfer to experiment with drones to measure the wave height from above. Sharp now works with HBO’s 100 Foot Wave documentary series, which has run to three seasons. He sticks to photogrammetry, which is the technique of measuring objects in a photo using other nearby objects—usually, using the surfer as a measuring stick. “It’s not, like, a space-age concept,” Sharp says.
But what does the size even matter? Let’s face it, it’s a cliché for a bro-dominated sport. The breathless media attention can make it seem like that’s all surfing is about—and overshadows a deeper, beautiful obsession at the heart of the sport. Surfers approach a wave with curiosity, in an attempt to enjoy it—or conquer it—but also to understand it, and learn from it. They watch waves endlessly, building complex, inarticulable intuitions. What matters is not only the height but how fast the wave is going, how thick its lip is, whether the barrel is hollow and rideable—and the lightbulb of understanding that it ignites in them. “Nalu is not only the Hawai’ian word for wave, but also translates to the word idea,” wrote Cliff Kapono, a professional surfer and scientist in an email. Slebir says there are 20-foot waves at Mavericks with a way bigger punch than 40-foot ones elsewhere. Summing up a wave by its height is about like summing up someone’s character by their height. But it’s still part of surfers’ love language for waves.
In other realms of human endeavor where wave size matters, people have developed perfectly serviceable measurement methods. “Not for bragging rights,” Özkan-Haller says. “It’s for safety, and building things.” Devices include: fiber-optic cables laid on the sea floor, anchored buoys, floating buoys, ship-mounted lasers, and shoreline-mounted synchronized video cameras (the U.S. Geological Survey has two cameras atop the Dream Inn in Santa Cruz to monitor coastal changes). What is a wave scientist’s take on surfers with video cameras? Better than nothing, Özkan-Haller says. “I would say it’s not the gold standard.”
Big wave as conveyor of joy (and fish)
In 1975, Jeff Clark was the first person in modern history to ride a Mavericks wave, and he surfed there by himself for fifteen years before anyone had the moxie to join him. Nonhuman surfers and swimmers have been coming to Mavericks for longer, though. Sea lions are sometimes seen popping up in the impact zone between waves. Harbor seals and bottlenose dolphins may also show up, according to Sue Pemberton, a biologist who has worked as a marine mammal monitor during the Mavericks contest. She once spotted a gray whale surface between heats. On iNaturalist, people have reported at least 11 species of mammals in the Pillar Point area. (In the third season of 100 Foot Wave, Nic von Rupp describes how sea lions helped his team find a wave off Cortez Bank, west of the Channel Islands.) White sharks turn up in the lineup from time to time, with all the drama that entails. Quite possibly, most have come for the fish: wave impact zones have lots of oxygen from all the churning and tend to be rich with marine life, according to Cara Field, director of conservation medicine at the Marine Mammal Center in Sausalito.
But some of the swimmers are frolicking. “I think it’s really amazing that some of these animals, like the dolphins and the sea lions, are just there to enjoy the waves—just like the guys and the gals are,” Pemberton says. “It’s a universal sport.”
Where a wave meets its end
Facing the brunt of the waves, on Pillar Point’s ocean side, are California mussels (Mytilus californianus)—the Alo Slebirs of the intertidal world. Even compared to other mussels, “California mussels need that really big wave action,” says Rebecca Johnson, the community science director at the California Academy of Sciences (who also chairs Bay Nature’s board of directors). They thrive on it. Their staying power comes from their beards—aka byssal threads, brown hairy tufts with sticky plaques at the ends. Byssal threads are stretchy shock absorbers, and so sticky that they’ve been studied for gluing wounds. Mussels send out more byssal threads as fortification during stormy seasons. Their shells are armor: the same calcium carbonate as chalk, but far tougher because it’s arranged microscopically in matrices, like bricks in mortar. Such adaptations allow them to dominate wave-swept shores in vast blue-black beds. But how do they cope with the biggest winter waves? Koehl, in an email, says she’s not sure. “I have never measured the forces on rocky shore organisms exposed to waves that big (for obvious safety reasons for myself and my equipment),” she writes. But one answer is that sometimes they perish. Big waves tend to chuck logs or other detritus, clearing swaths from the mussel bed. Which in turn makes space for new mussels or something else to move in, and transports dinner to some other lucky creatures.
For a tidepooler standing on the edge of the reef, the rogue wave appears as a violent surge of spray and danger. Yet Koehl warns us not to trust our intuitions about what this wave means for the reef’s tiny inhabitants, because our intuitions are developed from living life on a human scale. “Consider the flow from their perspective,” she writes. When Koehl placed flow sensors in intertidal areas, she found dramatic differences in the speed of water from spot to spot, and many refuges. Where water flows past a wall, it slows, building up what’s known in fluid dynamics as a boundary layer. A creature living in that slower flow needn’t be quite as tough as if it were sticking out into the main current, which may move 100 times faster. The shorter and more streamlined you are, the less tough you have to be: think limpets, crusty algae, sea stars. Other refuges abound in cracks and crannies and inlets, even between the spaces of barnacles or mussels. Places where creatures can get by without having to glue themselves down. Places where they can afford to be soft.
And in these varied flows, life has evolved many other ways to avoid getting swept away or destroyed by the flow (which they must balance with other needs, like eating and reproducing and not getting eaten). Sea spiders use hooks to stay on kelp with every step. Starfish have suction cups, and can lock their whole exoskeleton into a rigid position. Kelp, waving to and fro in swash, reduce yanking forces by growing longer; before they’ve unfurled their whole length on one wave, the water’s starting to flow back the other way. Snail mucus is a lubricant when the animal is moving—but miraculously, when the snail pauses, it becomes a glue.
Whether these organisms stand up to the wave or flow with it or hide from it, they all depend on it—the smorgasbord of food it brings, the waste disposal service it provides. Flowing water diffuses the chemicals that signal spawning-time, and swirls eggs and sperm together in orgy-clouds. It transports individuals to colonize new frontiers. It keeps them from baking. “Water is essential for life, and water is dangerous,” Koehl writes.
Measuring the ineffable
In September, at the annual Big Wave Challenge Awards in Newport, California, World Surfing League officials named Slebir winner of the Men’s Biggest Wave of the Year, based on three people’s photography and a video by Blakeney Sanford. But by WSL’s calculations—the methods were not released but attributed to “a team of scientists”—it was just 76 feet. The current record would stand at 86.4 feet (28.57 meters), set in Portugal in 2020. “The reaction it drew from the crowd was an audible wave of disbelief and cries of ‘bullshit,’” says Quirarte, who was there and felt WSL’s monetary interest tarnished its claim. More circumstantial evidence emerged to keep the debate alive, when scientists in Europe published an analysis of satellite imagery showing the largest swell ever detected from space—a 65-foot specimen—and estimating that in that same storm, waves might have reached up to 115 feet on December 21, 2024, two days before Slebir’s big ride.
One person did not seem to care about any of this, and that was Alo Slebir. “It’s kind of funny to measure waves, in my opinion,” he says. Every wave has its own unique power, and “it’s pretty much impossible to measure a three-dimensional force with a two-dimensional length.”
He might have gone further. A wave like that, like any big idea, is unknowable in its entirety. In the tidepool where it gurgles out, we can get a sense of how consequential the wave is, and how connected, with all the lives that encounter its energy. The lineup is another such place, for the brave. That Slebir cannot recall riding his wave is part of what makes the next one worth chasing. “I’ve got to go find it,” he says. “It keeps you wanting more. You want to remember.”
