What is a wave?

Waves can be fun. You can dive under them and jump over them. Watch them gently roll to shore or be awed by their power as they crash on the beach. So what are waves and how do they work?

How do waves form?

Waves are created by energy such as the wind. As the wind blows across the ocean passing through water it causes it to move in a circular motion.

Waves will form into a regular pattern of larger and smaller waves. The larger waves in the pattern are called sets. The smaller waves are referred to as the lull. The time between each wave crest is called the wave period and is measured in seconds.

Different conditions affect waves. It’s important to understand how waves work and what types of waves may be at the beach when you visit. Watch this video to learn more about how waves are formed.

  • Wind Strength: The stronger the wind, the bigger the swell.
  • Wind Direction: The wind needs to push the waves towards the beach for there to be surf. Sometimes beaches are also protected by headlands or reefs, which stop waves from reaching the beach.
  • Wind Duration or Fetch: The distance the wind has been blown over the ocean. The bigger the fetch, the bigger and cleaner the surf will be.

Breaking waves on the beach

As waves approach the coastline and move into increasingly shallow water they will start to slow down. There comes a point where the top of the wave overtakes it and starts to spill forward. The wave will then start to break. On any beach, there will commonly be a combination of three types of breaking waves. Each breaking wave has their own characteristics.
Dumping waves breaking on the beach

Plunging or dumping waves

Plunging or dumping waves create a hollow tube when they break. Surfers call this the ‘barrel’ or ‘tube’. Plunging waves are particularly dangerous as they can pick people up and ‘dump’ them onto shallow sandbanks or reefs with great force.
Image shows people standing in the water at the beach with the red and yellow flag

Spilling or rolling waves

Spilling or rolling waves are found where there are generally flat shorelines. They occur when the crest breaks onto the wave face itself. These are generally the safer types of waves to swim in.
Surging wave on rocks

Surging waves

Surging waves may never actually break as they approach the water’s edge as the water is very deep. They are commonly seen around rock platforms and beaches with steep shorelines. They are dangerous because they can appear suddenly and knock people over before dragging them back into deeper water.
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We are at the beach to help you. When you visit the beach come and see us and we can tell you about beach conditions and the safest place to swim.


What else would you like to learn about?

What is a rip current?

Rip currents are one of the biggest dangers at the beach. Knowing what a rip is, how to spot one and how to avoid one is key to staying safe at the beach.

Learn about marine creatures

There are lots of amazing marine creatures that live in the ocean and on our beaches. What are the ones you should look out for when you visit the beach?

What is a surf lifesaver?

Each summer over 20,000 members of SLSNSW put on the iconic red and yellow uniforms at beaches across the state. So who exactly are these heroes in red and yellow? Let's find out!

What is a wave?

Waves can be fun. You can dive under them, jump over them, watch them gently roll to shore or be awed by their power as they crash on the beach. So how are they formed?

How to stay safe at the beach

The beach is for everyone to enjoy. Knowing how to stay safe while at the beach will make sure that you and your family have the best day possible.