Answer: bobbing

AnswerCrossword Clue
BOBBINGLike a cork on a wave
bobbingBOB, to move quickly up and down
bobbingCause (something) to make such a movement
bobbing(of a thing) Make a quick short movement up and down
bobbingMove up and down briefly in a curtsy
bobbingMake a sudden move in a particular direction so as to appear or disappear