The boater was seen orbiting another person on the water at Barton Turf "while in possession of a machete" at about 9.45am on Tuesday.

At least three police cars and a forensics van were called to Staithe Road to investigate.

But the knifeman had already sailed off by the time they arrived, sparking a manhunt.

A police spokeswoman said that "no one was injured" and that "enquiries are ongoing" into the incident.

© Eastern Daily Press