The scientists studied how groups of waves behave in the surf-zone. They used experiments with cnoidal waves on a flat beach to see how the waves broke and changed in the surf-zone. They found that the way the waves grouped together affected where they started breaking. Inside the surf-zone, the wave groups looked different and affected the long wave motion. They developed a model using conservation equations and found that it worked well in the shoaling region but not in the surf-zone.