The attack happened on Chesterfield Canal between midday and 3pm yesterday (Tuesday, April 28).
Detective Inspector Craig Hall, of Nottinghamshire Police, said the force were treating ‘this unprovoked incident very seriously’.
"Officers are working hard to locate the suspect and to understand the full circumstances surrounding the incident,” Det Insp Hall added.
“The suspect is described as being tanned with black hair, of slight build, about 5ft 6ins to 5ft 8ins tall and was well spoken.
“Our enquiries are ongoing, including identifying any CCTV opportunities, and we’re urging anyone who may have been in the area around the time and saw what happened to please call Nottinghamshire Police on 101, quoting incident number 411 of 27 April 2021.”
You can also call Crimestoppers, free and anonymously, on 0800 555 111.