Two people had to swim to safety after being pushed into a canal by a gang of three men in separate attacks.
The gang first approached a man who was walking along a towpath that leads underneath Rainbow Hill, Lowesmoor, Worcester, on Sunday evening.
In the second incident the three assaulted a man before pushing him into the canal. Two of the offenders were pulled in with him.
Police described the incidents as "two alarming assaults".
The first incident took place between 1900 and 2000 BST on Sunday, when the man was pushed into the canal and swam to the other side.
In the second incident, between 1920 and 1930 BST, another man was walking along the towpath with a friend and walked past three men.
The man swam to the other side and got out before heading towards Tolladine Road.
His friend had run off and was not assaulted.
The three male offenders have been described as white and all about 6ft tall. Two had dark hair and the third had ginger or dark hair, police said.
All were between about 20 and 25-years-old.