Waves can either help or hinder the growth of river deltas, depending on how sediment moves along the shore and around the river mouth. A new model shows that when waves push sediment in a certain way, they can actually make delta channels grow outward instead of shrinking. This means that waves can affect how rivers build up sediment and change course over time. By understanding these processes better, we can predict how deltas will change in the future, which is important for managing and protecting these valuable ecosystems.