Sergeant Craig Enchelmaier from Sawtell police said the man was seen twice last Wednesday.
A Toormina woman, 49, saw the man as she was walking her dog at the reserve that day.
The man is described as aged about 30, with dark greying hair, unshaven, with a prominent nose and wearing a towel.
“We won't tolerate this type of behaviour,” Sgt Enchelmaier said.
“Help us put him in jail.”