In a mobile video taken at a Ganesha idol immersion near Mumbai, a policeman is attacked and his head is held under water by a volunteer. Nitin Dogade, in police uniform, is seen struggling with his attacker in an immersion pond, with a crowd watching them. When he comes out, three more assault him. Four men were arrested today for the incident that took place in Kalyan on Tuesday, more than a week after a traffic policeman was beaten to death in neighbouring Mumbai.