The science of surfing

All surfers spend long hours staring out to sea. They are not bored. They are studying. Slipping into the belly of these beasts and emerging alive requires decades of experience. You could be an exceptionally skilful, strong and courageous surfer but without a deep understanding of waves and how they travel from distant storm systems and react to complex interactions between wind, tide, current and bathymetry, the swells that break at Dungeons can kill.

“Experience is why you find slightly older guys out when it’s big,” says Marr. “Most of the guys are definitely early 30s to late 40s… it’s about being able to read the sea really well.”

Most big-wave surfers are towed into position by jet-skis but Marr is one of a radical few seeking to ride bigger and bigger waves by paddling alone. In doing so his margins for error are reduced to almost nothing. As a wave begins to gather, his years of experience and study are focused on a decision that must be taken alone and in only a few seconds.

“You are extremely calculated on the paddle,” says Marr, grinning. “A mistake doesn’t seem like a good idea. Because you wonder what would happen if you made a really bad one.”

Once Marr is committed there can be no going back. The biggest waves surfed at Dungeons are travelling at around 50km/h and to have a chance of catching them he must start in just the right spot and paddle hard. If he is too slow the wave will suck him into its maw and spit him out before sending him down to the dark, kelp-tangled depths. Waves as powerful as this can hold you down for so long that there is no chance of reaching the surface before the next wave comes crashing down. Local legend has it that Dungeons is so named because one of the first surfers to attempt to ride it suffered an extended incarceration.

If the surfer gets it right, however, the wave will bestow ecstasy. The memory of it glows in Marr’s eyes. Such a sensation is addictive and, like any junkie, Marr’s tolerance is growing. What was big once is no longer big enough. He is at a point when making a mistake and misreading the sea could be fatal.

Over 20 years of living in Hawaii and South Africa, Marr’s quest to tame ever-larger swells has meant that, like all serious surfers, he has become something of a scientist. He laughs and concedes: “I guess I am a bit of a climatologist.” Marr checks the weather charts twice a day if he’s working but otherwise every six hours, which is as often as they update. If he is expecting a swell he will be glued to the net. “It gets manic,” he says. “I start going through all the sites, the synoptic charts, the wave buoys, the models. I guess it’s nervous energy and you drive yourself mad.”

What Marr is trying to do is predict where, when and how that swell is going to hit the coast. He will form his hypothesis of where the biggest rideable wave will be, then get out there and test it by putting himself in its path.

A wave’s journey starts thousands of miles out to sea when huge low-pressure systems send high winds wheeling around, clawing and punching the water into hills and then blowing them into rolling mountains. Weather like this most often forms in the higher latitudes — the roaring forties, the furious fifties and the screaming sixties — where hurricane-force winds can blow for many days on end.

Inside a storm is a chaotic mess of waves, crashing from different directions at different sizes and at different wavelengths. But as the swells reverberating from the storm escape it, something mysterious begins to happen. The waves begin to form a rhythm, falling into step like soldiers on the march.

“The physics is extremely complicated and not well understood,” says the wave-tracking specialist Peter Challenor, of the National Oceanography Centre in Southampton. “It is probably to do with bigger waves parasitising the energy from smaller waves, grouping together with waves of a similar height.”

The waves form “sets”, groups of waves that travel at the same speed, allowing the storm’s energy to pass across the sea so efficiently that energy generated by winds off the Falkland Islands can be detected when the waves reach Cornwall. Although this energy is transmitted by waves, it travels faster than they do, forever creating new waves while waves at the rear of the set fade away.

Once the waves are on their way, their progress can be tracked. Wave-sensing satellites monitor sea levels with radar, incidentally detecting swells — a great boon to mariners and surfers alike. Wave buoys give a better indication of what is coming but cannot be trusted completely. “Wave buoys can’t measure the biggest waves,” says Challenor. “They go off the scale.” The buoys have elastic moorings that typically allow 30 metres of movement; a buoy is more likely to slide around the side of a huge peak than go over the top of it.

Physics used to predict that waves in the open ocean would very rarely exceed 15 metres, so that is the size naval architects design vessels to withstand. But the biggest waves to have been recorded — one in the midst of a hurricane in the Gulf of Mexico, one off the west coast of Scotland — have been twice that, the height of a ten-storey building. What is more, such waves are not as rare as was once thought.

“When waves are parasitising each other, you get some very weird, non-linear physics,” says Challenor. “From a relatively calm sea, suddenly a huge wave can just appear.”

There is another reason that the South African coast is notorious for its ship-destroying waves: it is where the swells from Southern Ocean storms meet the warm Agulhas current from the Indian Ocean, creating steep walls of water. By watching wave buoy readouts and the time that passes between peaks, surfers can calculate how long such a swell will take to reach the coastline.

Unlike sound waves, which travel at a constant speed, ocean waves with longer wavelengths travel faster. And when those long, fast waves — 25 seconds between peaks is promising for a big wave — start moving from the deep sea into shallower water, they begin to slow down. Speed is translated into height. Glenn Bee, one of the pioneers of big-wave surfing in South Africa, says: “Hawaii is so good for waves because the first time that the waves feel the bottom is only 100 metres from the beach.”

The Hawaiian islands are the peaks of mountains that rise from the deep sea. In South Africa, the continental shelf makes things more complicated. As the waves “feel” the bottom and slow, they start to refract. Bee says: “When the waves hit the shelf they create a lot of diversions. There are different channels all over the place… If the direction changes slightly, it can make the wave action totally different.”

In the mid-1980s, Bee was entranced by the giant waves that he could see breaking off the Cape. He and his friends tried to ride them but the swell was travelling so fast that they were often unable to catch it.

“We were struggling to get into the waves, not getting enough paddle speed to get down them… we’d get eaten a lot,” he says. That was when he and two friends came up with the idea of using an inflatable to tow themselves into position in front of the rising wave, as if waterskiing. Using heavyweight boards made from Agave cactus trees, they began to ride the waves they had dreamt of. Unbeknown to them, surfers in Hawaii had hit on the same idea and were using jet-skis to tow each other into waves.

Bee and his friends visited the oceanography department of the South African Navy. They left with reports and charts of swell, wind and current data, and observations of when certain spots had been seen to break. This information, used with bathymetric maps of the seabed, opened up tracts of South African coastline to big-wave surfing.

Bee admits, however, that they didn’t get everywhere. “I grew up near Gasworks,” he says, “which has the biggest, most perfect peak you’ve ever seen in your life. But it breaks on to exposed rock.” Make a mistake on take-off and that is where you would end up. “Back in our day we never even thought about it. Now guys are on it all the time. Surfing has progressed to such an incredible point.”

Facing the south west, where the storm swells usually originate, Dungeons gets the biggest waves. But that doesn’t make it pretty. In fact, surfers say, as a wave it’s downright ugly. The key to Dungeons’ character lies in two fangs of rock that pierce the surface at its back. Marr says: “They create an interesting bend and twist on matters. The wave is starting to feel the reef out there already so she’s refracting and doing all these interesting things already. Those outside mountains create a refraction that’s always slightly different.”

While a surfer towed behind a jet-ski can power away from a misjudged wave, Marr’s preference for the purity of paddling deprives him of that option. The bigger the wave, the longer the board he will need, in order to get the necessary speed and momentum. For a 30ft wave (which would have a 60ft face), he will be on a 10ft 4in dagger-shaped piece of fibreglass and foam. Marr can read off the width and the volume as easily as if he were telling you his birthday. If the board were a quarter of an inch different, he would feel it.

The wind can play a crucial role. Surfers usually like a gentle offshore breeze to make the faces of the waves steeper, but waves travelling as fast as those that break at Dungeons can create their own offshore wind. Marr says: “With big waves you need a little onshore wind, to make it easier for the wave to accept you.”

If it does, a glittering prize awaits. If it doesn’t, you are in for a brutal beating. “If you know something’s gone wrong, it’s important to get a breath in before you go down,” says Bee. “Pull your arms in, knees in. But I can remember many times not being able to do that. You can’t tell where your limbs are, you feel like you’re being ripped apart. It’s pretty intense.”

Dislocated arms and disjoined hips are common injuries. Snapped spines happen but drowning is the real danger. Big-wave surfers train with freedivers to endure “hold downs” beneath the wave. The best freedivers can hold their breath for more than nine minutes but surfers are as much interested in mental flexibility as physical endurance.

“It’s one thing to hold your breath for a long time, but it’s another when you get Mike Tyson whack you in the jaw then you jump into a huge washing machine,” says Marr. “It’s about getting used to the violence and not letting your heart rate come up. Because that burns the oxygen.

“In my worst wipeouts I’ve never even thought of breath. You’re getting so vandalised, you’re just trying to keep your arms and legs from getting torn off. Eventually it’s finished and it’s like, ‘Phew, some air would be lovely soon.’ But sometimes you’re super, super deep and you’re swimming and swimming and then you realise, ‘I’m going to have a two-wave hold-down.’ It’s important not to panic.”

It is bad news to be held so far under that you cannot surface for a breath before the next avalanche of ice-cold sea hits. A close friend of Marr’s, Sion Milosky, was killed earlier this year when he fell while trying to carve his way out of the bottom of a wave. He was fit and highly competent but he made a crucial error. He had taken on the first wave in the set. Behind that wave were eight or nine more monster waves. No one knows how many he managed to endure. The secret of survival, Marr says, is to take the later waves in the set.

Rogue waves can spell disaster for surfers, even if they have picked their spot carefully. Surfers can know where the swells they have been tracking will break. They can be in the right position to catch the expected wave. Then a monster can appear without warning. Another swell with a different wavelength or direction — perhaps two swells — have joined the first, creating terrifying unpredictability.

The way such a wave reacts to the seabed will be different from the ones that spawned it. It will often break in a solid wall of white water, across the bay. Called a close-out, in big waves this creates what is known in Hawaii as “Condition Black”, when all access to the water is banned.

The holy land, however, lies within the wave itself. To glide inside the barrel of a breaking wave, entirely surrounded by its enormous, spiralling energy, is the summit of the surfing experience. Marr says: “It’s like being inside a tornado, but being able to stay in control.”

When a wave suddenly hits shallow water, it trips. Until then the water has been transmitting energy, its molecules travelling in a circle. Contact with the seabed slows the lower part of the wave, while the lip keeps its momentum and spills over the top. If the structure of the reef — and the wind, the swell direction and more — are perfect, the lip of the wave is propelled forward, arcing over like a waterfall, leaving a hollow beneath. When a big wave forms a barrel particularly quickly, it creates a patch of low pressure. The wave inhales sharply, sending a stinging spray into the surfer’s face. Then there is a pause.

“Inside, time slows down so much, you’re so in the moment and each little water droplet makes sense,” says Marr. “You’re incredibly focused on the water sliding past the rail of your board. You’re going so quick.”

Speed is of the essence. Behind you stalks the “foam ball”, a furious eye of white water that guards the back of the tube, snapping at your board. Ahead of you is the leading edge of a curtain of water that is cascading over your head. When the barrel starts to collapse, it exhales, launching the surfer out in a giant roar of spray.

“You feel so lucky,” says Marr. “Through experience and the love of what you’re doing, you can time things so perfectly that you can ride inside this incredible force of nature.”

Life of an ocean wave

Creation: Capillary waves

In a depression far out at sea, wind blows horizontally above calm water. But random disturbances (mini-vortices) blow downwards, pushing into the ocean and creating bumps.

Evolution: Gravity waves

Some mini-vortices chase capillary waves, adding energy and turning them into ripples. As the wind’s grip increases, larger vortices (turbulent eddies) make the waves grow.

Propagation I: Free-travelling swell

Gravity waves are limited in size only by gravity and wind. As they are driven away from the depression (storm centre) by the wind, they become free-travelling swell, still free from interference from the sea bed. These large waves have been known to travel for 15,000km.

Propagation II: Dispersion and grouping

The waves may undergo changes as they travel. In circumferential dispersion, they lose energy and height as they spread out, in theory roughly half of their energy and 30 per cent of their height for every doubling of distance. In radial dispersion, longer waves travel faster than shorter (steeper) ones. The waves also arrange themselves into sets (groupings) as trains of different wavelengths mix.

Refraction: Effect of the sea floor

As the ocean gets shallower, waves are influenced by sea floor topography (bathymetry). This makes them bend — refraction. It occurs because waves slow down in shallow water (eg, reefs or beaches), while any part of the wave in deeper water (eg, channels) does not. The bit in the middle (transition zone) bends towards the shallower water. Refraction causes waves to lose height, making them longer and more lined up.

Breaking I: Why waves break

As the waves slow down in shallower water, their speed is directly related to the depth: the less water there is beneath them, the slower they go. But this means that the top of a wave travels faster than the bottom, eventually overtaking it and causing the wave to break.

Breaking II: How waves break

A typical wave breaks at a depth that is 1.3 times its height. How they break depends on how they reach very shallow water. If a wave suddenly hits very shallow water (eg, a reef), then the top will be going much faster than the bottom, making the wave “throw out”. This is a plunging breaker, the kind that forms “tubes”. Spilling breakers, which have a shorter wavelength, occur when the transition is gradual. As soon as the top of the wave goes faster than the bottom, they spill over, creating a foamy head.