Olivia Hope's father has some questions for the man jailed for her killing, after reading a new book about the case.
Watson is serving 19 years for killing the 17-year-old and Ben Smart after a 1997 New Year's Eve party in the Marlborough Sounds.
Elementary-- The Explosive File on Scott Watson and the Disappearance of Ben and Olivia, written by journalist Ian Wishart, is due out tomorrow and purports to have found the mystery ketch in the case.
Mr Hope told Newstalk ZB the book provided the most balanced account he'd seen about whether Watson was the murderer.
Listen: Gerald Hope speaks to Newstalk ZB's Chris Lynch about the new report
He said Mr Wishart's book opened his eyes to some of the evidence that wasn't used in the trial.
The Herald revealed today a report by the Maritime Research Group which includes a photo of a blonde woman on the back of a runabout on January 5, 1998, which the authors say is Olivia Hope.
He said an apparent sighting of his daughter five days after she was supposed to have been killed was unconvincing.
Mr Hope received a copy of the report in 2011 but said he can't see a link to his daughter.
Mr Hope didn't think the report included enough evidence to suggest the second mystery ketch existed.
He also didn't think the photo which the Maritime Research Group claimed was Olivia was clear enough to positively identify.
But he believed the group's hypothesis, importantly, took the investigation in a new direction.
"It's given clarity in some aspects."
The group's report paints the ketch as having a central role in the smuggling of cocaine.
The suggestion of a drug syndicate's involvement in the murders was "chilling", Mr Hope said.
"It scares the sh*t out of me. This stuff obviously goes on but it's a sector most normal New Zealanders have nothing to do with; let alone understand how it operates.
"The scale of what they're proposing there; the quantities of cocaine being imported [is] chilling."
Mr Hope believed there were two questions in particular which still hadn't been answered.
Watson might be able to fill some gaps, he said.
"Scott Watson is key to all this. He's been in jail for 19 years; there's questions I have to ask him and hopefully I'll have the opportunity to.
"At the end of the day, all we want to do as a family is demystify the disappearance of Olivia and Ben."
That resolve would come when it was clear in everyone's mind what happened on January 1, 1998, he said.
Finding Olivia and Ben's remains was also important to the family.
"[Olivia's] dreams and expectations were never realised, nor were Ben's.
"A quarter of our family had its heart ripped out. That ripple effect has been with us for the past 19 years. It does damage people and it changes your view of society and changes your view of relationships.
"My belief is there's people out there that definitely have information that could assist us."