Department of Conservation marine scientist Clinton Duffy, who has written a paper about the occurrence of manta rays in New Zealand waters, said the sighting was a treat because, although they migrate here each year, they are rarely seen.
"The species that we see in New Zealand has never been recorded from the southwest of the Pacific or anywhere in the western Pacific.
"They're quite rare visitors. Although they do come here every year, they are actually very rare - there's not large numbers."
Mr Duffy said the manta ray was special in that it could grow up to 10m in width and did not have a sting and therefore could not hurt you that way.
"The only danger they really pose is if they land on you by accident, because they do jump," he said.
"They exceed a tonne ... You could be killed if one landed on you.
"But it's never happened - that I know of."
MANTA FACTS
* Can weigh more than a tonne.
* Can grow up to 10m wide.
* Does not have a sting.
* Has only one pup every other year.
* Is completely protected in New Zealand waters under the Wildlife Act.