Police were called out just before 10am, when a member of the public made the discovery.
It is understood the person who came across the body saw it floating in the water and went out to bring it back to shore.
Inspector Matt Rogers said: "A young lady was found face down in the water. At this stage, we don't know who she is, we don't know the circumstances as to how she's come to be in the water."
Mr Rogers said there had been no missing persons reported in the area and they are now making moves to find her family.
He would not give any clues about the woman's appearance or her clothing, but said police would reveal an identikit photo in the next few days if no one came forward.
Officers cordoned off a part of the beach where the body was found.
Kaumatua from the local iwi were also at the scene to bless the site.
Police said there were no forms of identification on the woman and initial checks have not revealed any recent reports of a missing person that fit her description.
Further information will be made available once additional inquiries have been carried out.
