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Alucia, believed to be owned by American billionaire investor Ray Dalio, berthed at the T/U sheds in Dunedin between 9am and 10.45pm.
The 56m megayacht had reportedly travelled from Lyttelton and departed Dunedin for Bluff.
It was the only ship in the world to carry three deep-diving manned submersibles and was once used by film-maker James Cameron to discover the remains of Titanic.
Alucia was also used on a special expedition to film giant squid.
A French-built submarine support ship, Alucia was reportedly sold to Dalio in May 2011 for $38 million.
It had been completely rebuilt and included a helicopter pad, submersible hangar, decompression chamber, mixed-gas dive support, powerful sonar and a luxury interior - able to accommodate 16 guests.
Mr Dalio founded hedge fund company Bridgewater Associates and last year was named in Time magazine's list of the 100 most influential people in the world.
According to Forbes magazine, he was the 44th richest person in North America and the 88th richest person in the world, with a net worth of $US10 billion as of March 2012.
His aim in buying Alucia was to provide the boat to scientists and film crews for oceanographic research.
It was unclear yesterday whether Alucia's visit to Dunedin was merely a pit stop for crew, or if it was berthed in the city for business.