A fish, when deceased, ceases to follow anything. Following requires a conscious act of animus. The reaction of the mortal remains of the late finned being to being pushed around by the force of the tide/currents is to go with the flow. It cannot do anything else, being deprived of ability to move any part of its anatomy to counter said force. I did think to say its sole had been gathered up by Almighty Cod, but on reflection will forebear from so doing.