She was then taken to hospital in an ambulance.
The rescue vessel’s captain, Lovro Oreskovic, said Ms Longstaff was “exhausted” when she was found on Sunday, adding: “We were extremely happy for saving a human life.”
According to the Sun, Ms Longstaff told one rescuer it had helped that she was fit from doing yoga and that she sang to stop her feeling cold overnight.
David Radas, from the Croatian Ministry of Maritime Affairs, said rescuers were able to work out the exact moment Ms Longstaff fell in the water by checking CCTV from the 965 ft long( 291 m) cruise ship.
“Because they knew the time, they were able to know the exact position of the ship, ” he told the paper.
Mr Radas told the BBC Ms Longstaff was hypothermic, but overall in “good physical shape” when she was found.
He said the circumstances around how she decreased from the Norwegian Star ship were being investigated.
The Croatian Coast Guard said a ship and an aircraft launched a search at around 06:30 local hour on Sunday.
The ship’s crew spotted Ms Longstaff in the sea – around one mile from where she fell – at 09:40 and one of the crew dived in the high seas to haul her out before taking her to shore.
The Norwegian Star was delayed getting to Venice on Sunday, having also been part of the search operation in the early morning.
“The ship merely told us a passenger fell overboard and we expended a few hours searching for her, ” passenger Bethany Joyce told the BBC.
The 21 -year-old from Long Island, New York is currently in Venice with her family, after missing their flight to Toronto on Sunday.
She said disembarkation was “a mess”, adding: “( We) understand it was very hectic for them but we think it could have been handled much better.”
A statement from Norwegian Cruise Line confirmed that a guest had gone overboard while the ship was on its way from Vargarola to Venice.
It said: “We are pleased to advise that the guest was procured alive, is currently in stable condition, and has been taken ashore in Croatia for further treatment.
“We are very happy that the individual, who is a UK resident, is now safe and will soon be reunited with friends and family.”
The Foreign Office corroborated it had been notified of the incident.
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