When the skull was found three years ago, it was originally thought to be male, perhaps belonging to Alan or Donald Anderson, whose trawler capsized in the area in 1996.
But Otago University scientists Jules Kieser and John Dennison, who were handed the remains by police in June, concluded it was female.
Now Olivia's father, Gerald Hope, is demanding to know why police held onto it for three years without letting his family know.
"It would have been nice to be told about it, even if it was to say it was irrelevant," he said.
Mr Hope is pushing for a DNA test to determine whether it belonged to his daughter.
He heard about the latest find through the media, and intends to contact the head of the inquiry, Detective Inspector Rob Pope, today.
Mr Pope could not be contacted last night.
Professor Kieser told the Herald the skull belonged to a small-boned woman. His colleague had said the thinness of the bones indicated she might have had anaemia.
A deep-water barnacle, which can be aged due to calcification and incremental lines on its shield and base, has been sent for further tests.
Professor Kieser said barnacles usually attach to body parts when they are clean of flesh, which is removed by decay and fish.
Bodies tend to decompose about 30cm under the water, and can drift for weeks because fat is lighter than water. Once the flesh decays, they sink down and settle.
Professor Kieser said the skull was intact, but lacking teeth and some facial bones.
It could not, therefore, be identified by dental records or facial-mapping from a photograph.
Only DNA testing could determine its identity.
Marlborough Sounds harbour- master Alex Van Wijngaarden said the currents from the Sounds generally run up the coast, not down. However, it could not be ruled out that remains could end up in Canterbury.
But, he said, in Tory Channel the currents run at seven or eight knots, and the direction constantly changes with the tide.
The Waimakariri River is a long way away, but it is "impossible to predict where remains would end up".
"In all my time at sea, I have learned that you cannot discount anything."
Chris Watson, who with his wife, Beverley, has led a four-year campaign protesting the innocence of his son Scott - now in Paremoremo prison serving a life sentence for the murders of Ben and Olivia - told the Herald that the latest discovery is yet another "what if".
"It keeps people looking outside the square, and that's good. It goes on the list until it is crossed off."
The Sounds murders
