expression, noun or participle which takes 'suru'
bobbing up and down; rising and falling
Describes something repeatedly moving up and down, often on water or in a fluctuating situation. Used as a set phrase, often with する.
小舟が波に浮きつ沈みつしている。
The small boat is bobbing up and down on the waves.
彼の気分は一日
His mood was rising and falling all day.