The incident occurred in bushes near the boating lake between 4pm and 5pm on Saturday 5 October 2019.
A man aged in his 30s was arrested nearby on suspicion of outraging public decency and possession of class A drugs. He has been released on conditional police bail while enquiries continue.
We are requesting the public’s assistance to help establish the full circumstances surrounding the incident.
Police are appealing for information about the behaviour of a man described as white, aged 35 to 40 years old with yellow hair who was wearing a dark jacket, grey tracksuit bottoms and red trainers.
If you wish to remain anonymous, you can pass information to Crimestoppers on 0800 555 111.
Please quote the North Yorkshire Police reference number NYP-05102019-0357.