The 7.5m yacht they were on, which disappeared in Foveaux Strait almost two years ago, set sail from Bluff on April 16, 2014 despite a stormy weather forecast.
The two tourists were 19-year-old German students Veronika Steudler and Lea Tietz. The skipper was dairy farm worker Andrew Kinzler.
The coroner said it was "clear that Andre Kinzler was an inexperienced yachtman" who had relied on YouTube videos for at least some of his training.
Mr Kinzler's "lack of radio skills and experience" was also found to be a "concern".
During the inquest, the coroner heard from Bluff Fishermen's Radio operator Marie Leask that Mr Kinzler was a "poor communicator" who did not seem to understand the fisherman's radio service system or why it was important to tell her where he was going.
It was not clear whether Mr Kinzler knew about the "unfavourable weather forecast for the Foveaux and Puysegur areas at the time he was intending to sail in that area".
Nonetheless, the coroner found, it was Mr Kinzler's responsibility to stay abreast of the weather forecast, which was gale force winds, high seas, rain and poor visibility when he set sail from Bluff.
It was also his responsibility to ensure his boat, the Munetra was "adequately provided with communication equipment". It was not, the coroner found; Mr Kinzler had only a mobile phone and a hand-held radio.
The coroner said the fault lay with Mr Kinzler alone, not with "any person or organisation, including [Maritime New Zealand], Bluff Marine Radio, or Mari Leask".
"The information was there for Andrew Kinzler to obtain and receive; he ignored the warnings given to him," the coroner wrote.
As a result, the coroner found, the Munetra had sunk in the Foveaux Strait, "probably on 16 April 2014".
