Ben Smart and Olivia Hope were two young New Zealanders who were murdered in the early hours of the morning on New Year's Day, 1 January 1998.
The two friends had been celebrating on New Year's Eve at Furneaux Lodge in the Marlborough Sounds with other partygoers.
They accepted an offer from a stranger to stay aboard what he said was his yacht, and all three boarded the vessel at a time estimated between 4 a.m.
and 5 a.m.
It was the last time the pair were seen, and their remains have never been found.
Police investigations began on 2 January 1998, after Smart and Hope's parents reported them missing.
In the following months, police came to believe that the unidentified man was Scott Watson (born 28 June 1971).
Police charged Watson with murder and, after an eleven-week trial, he was convicted and sentenced to life imprisonment with a minimum non-parole period of seventeen years.
Watson still protests his innocence; however after fruitless efforts, all avenues of appeal have failed.