The Germanic languages are traditionally divided into three groups: West, East and North Germanic. They remained mutually intelligible throughout the Migration Period. Dutch is together with English and German part of the West Germanic group, that is characterized by a number of phonological and morphological innovations not found in North and East Germanic. The West Germanic varieties of the time are generally split into three dialect groups: <answer>Ingvaeonic</answer> (North Sea Germanic), Istvaeonic (Weser-Rhine Germanic) and Irminonic (Elbe Germanic). It appears that the Frankish tribes fit primarily into the Istvaeonic dialect group with certain <answer>Ingvaeonic</answer> influences towards the northwest, still seen in modern Dutch.
What's the West Germanic dialect spoken in the North Sea region called?
Ingvaeonic