On Sunday afternoon, the small bone, believed to be human, was discovered by passers-by in the vicinity of Flynn’s Beach.
It has been seized by police and will be subject to forensic examination, with any results being compared with missing person records.
Bones belonging to one or more humans were discovered at Port Macquarie beaches last month.
A spear fisherman contacted police on Saturday June 15 after finding a bone in the water at Flynn’s Beach. No other items were found during a search a day later.
More bones were found by another spear fisherman at nearby Flat Rock, east of Nobby Head, on Monday June 17.
Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au.