The study looked at how certain types of waves called infragravity waves affect the movement of sand on a beach in the Netherlands. These waves have a specific period and can carry sand in the water. By studying the beach for five weeks, the researchers found that infragravity waves play a significant role in moving sand in the surf zone. They discovered that the direction and amount of sand movement by these waves depend on where you are in the surf zone. In some parts of the surf zone, the sand moves towards the sea, while in others, it moves towards the land. Overall, the researchers found that infragravity waves are just as important as regular waves in moving sand on the beach.