The Physics of Surfing for Beginners – Part I

Why is the physics of surfing for beginners important to learn? 

How does surfing work?

Where do the waves come from?

How is it possible for surfers to catch waves?

Surfing is one of the most unique experiences in the world.

Thereʻs no other sport quite like it and that is due to the dynamics of wave riding. When you stand up on a wave, you are balancing on a moving board that is being powered along by a wave of moving water. Which is why we will teach the physics of surfing for beginners. 

With skating and snowboarding, at least one plane is fixed in place. With surfing, two planes are fluid and open to infinite possibilities.

The purpose of this blog is to help beginner surfers understand the basic nature of surfing waves.

If you are new to surfing, or if you have some experience (maybe mostly with falling – hey, no judgment), this blog will help illustrate how waves work and how you can use this knowledge to catch more waves and have better, cleaner, longer rides.

This blog breaks down the nature of ocean waves, surfing waves, the difference between groundswell and wind-swell, bathymetry, and the physics of breaking waves.

What are waves and how are they made?

Water + energy = waves

The waves that we see at the beach are not static – a trip to the beach does not guarantee that you will see waves breaking in the ocean.

The cycle of waves rolling across the globe is created by forces of energy.

Ocean waves are not “born” and they do not “die”, at least not in our understanding of these words. It is a law of physics that energy cannot be created, nor destroyed. Instead, energy is continuously changing forms. Just like the waves you see at the beach.

Energy cannot be contained, either. It moves outwards. This is why when there is an earthquake, a tsunami alert follows. Once the energy is mixed with the water, there is a ripple effect. These waves go on to travel around the globe until they hit land. 

There are many different types of waves – sound waves, light waves, etc. – and they all obey the same basic laws of physics.

Ocean waves have some key physical properties – amplitude, wavelength, and frequency – that we can observe before paddling out to surf.

The amplitude of a wave refers to its height.

The wavelength is the distance between wave crests.

The frequency of waves refers to how many waves come in a set.

The physics of surfing for beginners is important. Observing all of these different properties before you paddle out is useful because it helps you make the most out of your surf session. Next time you check your local surf report, notice that it includes these measurements.

How do waves get big enough to surf?

The wave breaking and curling behind a surfer is the force that drives the surfboard down the line.

This kinetic energy is all that is needed for surfing. However, the ocean isn’t constantly churning out waves that can be surfed. It is not a given – conditions change all the time. To have waves that we can surf requires the right combination of swell, wind, tide, in addition to having an ocean floor suitable for breaking waves.

Wind-swell v. Groundswell

Groundswell

Did you know that some waves travel as far as 9,000 miles (15,000 kilometers) across open ocean before they become the curling wave that surfers look to ride?

Since we can measure wind speed, direction, and waves, we can determine when there will be a swell coming to our local surf spot.

The waves that come rolling onto shore in clean lines, widely spaced apart, usually indicate that they have traveled a great distance.

These waves are referred to as “groundswell” and make for the most ideal surfing waves. With this type of wave, you can paddle out with little to no wind and still catch some amazing waves.

That is because groundswell is generated from far away and the longer it takes to roll into your local surf spot, the more time the waves have to get organized into a consistent shape and pattern.

Along the way, waves will form into separate and distinct groups, referred to as a “set” of waves. From shore, you can easily observe the sets and count the frequency of waves in each, the time (typically in seconds) it takes one set from start to finish, and the lull period in between sets.

Wind-swell

Wind = energy, so wind + water = waves

“Wind-swell” refers to waves generated by local wind conditions.

These kinds of waves are usually choppy, small, messy, and only give surfers a short ride, but that doesn’t mean that windy conditions canʻt work in a surferʻs favor.

Depending on the location and wind direction, wind-swell can actually make some spots that are less popular for surfing more fun.

However, remember to keep in mind that if you are paddling out on a windy day – wind-swell usually means you will have to do more paddling in order to keep yourself properly positioned in the lineup.

When and why do waves break?

Surfers want waves that peel left or right, rather than waves that close out immediately after cresting.

That is because surfers ride waves and there is not much to ride if the waves are closing out. For those learning how to surf, this can be very important to know before paddling out.

Whether it be breaking left or right, you want to look for waves rolling in that have crumbling white water pushing a blue face in towards shore.

Beach breaks are often closeouts, dumping waves onto the shore in one swift barrel before becoming whitewash. Why? Because the momentum of the wave above water is moving faster than the underwater wave, which eventually causes the crest to tip over all at once.

With peeling waves, the wave you see above water is tipping over at a more gradual pace, slowly working up the length of the wave.

For surfers, this makes for better surf because it means momentum in two dimensions – forward, towards shore, and along the shoulder of the wave breaking either to the right or the left. This gives surfers the opportunity to do carves, pumps, cutbacks, and other interesting maneuvers.

What is bathymetry and why do I care?

Bathymetry is the science of underwater depths existing in natural bodies of water.

Whereas topographic maps show us the shape and elevation of land, bathymetric maps show us the shape and depth of the ocean floor.

Knowing what lies beneath the surf is just as important as knowing how big the surf will be when you paddle out.

When a wave rolls in from the open ocean and hits a reef bed sitting on the ocean floor, the wave will begin to break on the side that hits the underwater obstacle first. Voila – you have a peeling wave.

If you are surfing at a sandy bottom break that has little to no change in underwater depth, then there is nothing underwater to interrupt the momentum of the wave as it moves in towards shore.

Beach breaks and other closeout waves simply donʻt last long enough for a surfer to do any surfing beyond popping up.

As soon as you stand up, you get tackled by the curl and thrown over the falls. While dumping closeouts can be fun for body surfing or bodyboarding, it is not the right kind of environment for beginner surfers who want to practice riding waves.

If you want to keep reading about the science of surfing waves, stay tuned for Part II!

Ready for your first surf experience? Book a lesson with HOKALI!

To continue reading about the physics of surfing for beginners, check out this blog!