White-beaked dolphins are boisterous swimmers and like to surf in the waves of ship bows. They live in groups of six to twenty animals. Since around 1955, the white-beaked dolphin is seen regularly in the North Sea. It is presently the most common dolphin species in the North Sea. There are probably between 7000 and 8000 white-beaked dolphins swimming here. Scientists have seen a decline in recent years. It is still unclear; however the warming up of the seawater is seen as a possible cause.