Swell with Surfing: Learn Formation, Development, and Dissipation

by Joost Nusselder | Last Updated:  08.02.2023
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With surfing, you can’t just get any old wave, you need the right one. A wave that’s just right for you to ride. So what is a right wave? A swell.

A swell is a wave that’s generated by a meteorological phenomenon (surface gravity waves), which originates in the sea. They’re not generated by the immediate local wind, instead by distant weather systems. As it approaches the coast, it becomes a wave with special characteristics that allow it to be ridden.

In this article, I’ll explain everything you need to know about swell with surfing, including what it is, how it’s formed, and how it affects the waves you ride.

What is a swell

What is Swell in Surfing?

What is Swell?

Swell is a term used by surfers to describe a set of waves that have been generated by a storm or weather phenomenon in the ocean. It’s the wave that forms when the mass of water hits a point where the ocean is less deep. This movement creates waves that can be ridden when they reach the shore.

How Does Swell Affect Surfing?

Swell is affected by the winds and tides of the area it’s generated in, as well as the time of day and weather conditions. This means that the waves can be different depending on the conditions, so it’s important to know what to expect before heading out to the beach.

Tips for Enjoying Swell

If you’re looking to make the most of swell, here are a few tips to keep in mind:

  • Check the weather and tides before heading out to the beach.
  • Choose the right board for the conditions.
  • Be aware of your surroundings and other surfers.
  • Have fun and enjoy the ride!

So if you’re looking for an adrenaline-filled experience, why not check out the swell and see what it has to offer? With the right preparation and knowledge, you can have an awesome time out in the waves.

Surfing 101: A Beginner’s Guide to Waves, Swells, and Breaks

Understanding Swell

Surfers know that the sun is the source of all good waves. Solar energy creates wind, and winds blow across vast areas of open ocean to create energy that eventually organizes itself into swell. Swell can travel for thousands of miles, and the wave energy can reach up to 1,000 feet in depth.

When swell travels great distances or combines with other swells, it can increase in size and interval. There are two types of swell that cause surf:

  • Groundswell: Created by large storm and weather systems or strong wind blowing over long distances of open ocean. Groundswell often creates large and powerful surf.
  • Wind swell: Created by less powerful, more localized wind systems. The wave energy from wind swells do not run as deep, and they only travel short distances across open ocean.

Understanding Wave Formation

When swell finally reaches shallow water – whether that be a continental shelf, a reef system, or a sand bar – it is slowed and finally releases its energy in the form of breaking waves. When swell bends horizontally as it breaks, it is called refraction. Refraction steers swell towards or away from shore.

There are two types of refraction that can occur, depending on the ocean floor topography:

  • Concave refraction: When open ocean swell comes into contact with an abrupt, protruding change in the ocean floor that is surrounded by deeper water – often a reef or sand bar – the swell will bend at its far ends as it turns into a breaking wave. The result resembles a bowl shape that travels towards the shore, with the “opening of the bowl” facing the shore.
  • Convex refraction: When open ocean swell collides with a protruding headland, such as a cliff, jetty, or even a pier, the portion of swell confronting the headland slows, while the rest of the line of swell continues forward at pace. The result closely resembles a “C” shape with the curved side moving towards the shore.

Understanding Surf Breaks

When swell reaches shallow water, it releases its energy in the form of breaking waves. Surf breaks are categorized in three different ways: beach breaks, reef breaks, and point breaks.

  • Beach break: When swell hits a beach, it creates a beach break. Beach breaks are great for beginners because they are usually mellow and forgiving.
  • Reef break: When swell hits a reef, it creates a reef break. Reef breaks are usually more powerful and can be dangerous for inexperienced surfers.
  • Point break: When swell hits a point, it creates a point break. Point breaks are usually long and powerful, and they can be great for experienced surfers looking for a challenge.

Wave Anatomy

No two waves are alike, and the same is true for wave setups. To improve your surfing skills, you need to understand wave mechanics and have an in-depth knowledge of different types of surf breaks. Here are some of the key components of a wave:

  • The Shoulder: The shoulder of the wave is the part of the wave that is just beginning to break.
  • The Face/ Wall: The face of the wave is the part of the wave that is breaking.
  • The Lip: The lip of the wave is the part of the wave that is curling over.
  • The Channel: The channel of the wave is the part of the wave that is running down the line.

What is Ocean Swell?

Have you ever been to the beach and noticed the waves crashing against the shore? That’s ocean swell! Ocean swell is created by distant weather systems over the ocean and is made up of five factors:

Wind Speed

The wind must be moving faster than the wave crest in order for energy to transfer from air to water. The stronger and more prolonged the wind, the bigger the waves!


Fetch is the uninterrupted distance of open water over which the wind blows without significant change in direction.

Width of Water Surface

The wider the water surface, the bigger the waves!

Wind Duration

The longer the wind blows over the fetch, the bigger the waves!

Wave Dimensions

When describing a wave, there are three dimensions to consider: wave height (from trough to crest), wave length (from crest to crest), and wave period (time interval between arrival of consecutive crests at a stationary point).

Deepwater Wave Effects

When waves reach shallow water, they can cause movement of water particles, known as Stokes drift.

So the next time you’re at the beach, take a moment to appreciate the power of the ocean swell!

How Swell Waves Form

The Science Behind It

Have you ever wondered how those long, majestic swell waves form? Well, it’s all thanks to the genius of Klaus Hasselmann, the 2021 Nobel Prize winner, who figured out the non-linear effects that cause them.

Basically, two wave trains in deep water can interact to create two new sets of waves – one with a longer wavelength and one with a shorter wavelength. This process is now used in sea state models, like Wavewatch III, to help predict the weather and climate.

A Visual Analogy

It’s a bit tricky to explain the Hasselmann process in words, but here’s a helpful visual analogy:

  • Think of the short waves as a swing, and the long waves as the person on the swing.
  • Each small breaking wave gives the swing a small push, just like a person pushing the swing at the right time.
  • There’s no comparable effect in the wave’s trough, which would reduce the size of the long wave.

The Bigger Picture

So, what’s the big deal? Well, the wind sea and the swell have a huge impact on transferring heat from the ocean to the atmosphere. This affects both large-scale climate systems, like El Niño, and smaller-scale systems, like the atmospheric depressions near the edges of the Gulf Stream.

And it’s not just ocean waves that follow this pattern – you can also see it in the sorting of sand grain sizes on a beach. It’s a fascinating process that shows how random wave fields can generate order, even though energy is lost and disorder increases. Pretty cool, right?

The Dissipation of Swell Energy

What is Swell Energy?

Swell energy is the energy created by waves in the ocean. It’s what gives us those awesome surfable waves we all love. It’s created by storms and can travel long distances, giving us waves from far away.

How Does Swell Energy Dissipate?

Short waves dissipate quickly, which is why swells from distant storms are only long waves. But even long swells lose energy over time. Here’s how:

  • Long swells lose half of their energy over a distance of up to 20,000 km (half the distance round the globe).
  • The rate of energy loss is determined by the swell steepness, or the ratio of the swell height to the wavelength.
  • It’s possible that the energy loss is due to friction at the air-sea interface.

So What Does This Mean For Us?

Basically, it means that we can get some awesome waves from far away storms, but they won’t last forever. So if you see a swell coming, make sure to get out there and enjoy it while it lasts!

Understanding Swell Dispersion and Wave Groups

What is Swell Dispersion?

Swells are like the ocean’s version of a long-distance phone call – they start off in one place, but can travel thousands of miles before they reach the shore. This means that by the time they reach the beach, the waves have had plenty of time to sort themselves out and get rid of any choppiness.

How Does Swell Propagation Work?

When a storm kicks up, the waves it creates have the same speed and will travel together in groups. But if the waves are even a fraction of a meter slower, they’ll lag behind and arrive much later. The amount of time it takes for the swells to reach the coast is determined by the distance from the storm and the wave period.

For example, if a storm is located 10,000 km away, swells with a period of 15 seconds will arrive 10 days later, followed by 14 second swells 17 hours later, and so on.

What Can We Learn from Swell Dispersion?

By looking at how the peak wave period decreases over time, we can figure out how far away the swells were generated.

In the storm, the frequency spectrum of the sea state has a well-defined peak with dominant frequencies within 7% of the peak. But as the swells travel further away, the spectra become more and more narrow, sometimes as low as 2%. This means that wave groups (aka sets) can have a lot of waves – from 7 in the storm to 20 or more in swells from distant storms.

What Are the Effects of Swell Waves on the Coast?

What are Swell Waves?

Swell waves are the big, bad boys of the wave world. They’re the ones that come from far away and pack a punch. They’re the ones that can make even the most experienced surfer feel like a tiny speck in the ocean.

How Do Swell Waves Affect the Coast?

Swell waves can have a big impact on the coast. Here’s how:

  • They transfer more energy than shorter wind waves, thanks to their longer periods.
  • They start refraction (the process of bending waves) further out to sea, since they have longer wavelengths.
  • They can be hard to spot, since they mix with normal sea waves.
  • They can cause a lot of damage to the coast if they’re bigger than normal waves.

What Can We Do About It?

The best way to protect the coast from swell waves is to be prepared. Here’s what you can do:

  • Monitor the swell waves in your area and be aware of any potential risks.
  • Take extra precautions when the swell waves are bigger than usual.
  • Make sure your home is secure and your belongings are safe.
  • Talk to your local authorities and ask them what measures they’re taking to protect the coast.


So there you have it, everything you need to know about swell with surfing. Now you’re ready to get out there and catch some waves! Just remember to keep an eye on the wind and remember to use your gut feeling to decide when to go.

Joost Nusselder, the founder of Kauai Surf Report is a content marketer, dad and loves trying out new sports with everything surfing at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2019 to help loyal readers with surfing and water sporting tips.