The passenger, named in reports as Kay Longstaff, was pulled from the Adriatic Sea on Sunday morning, having fallen from the back of the Norwegian Star as it sailed 60 miles off the Croatian coast on Saturday.
The woman, who gave only her first name, Kay, spoke to reporters shortly after her rescue ship arrived at a Croatian dock.
Clay Barclay, who was onboard the Norwegian Star cruise vessel, posted an image to social media of the section of the boat where the woman fell over.
She told Croatian news channel HRT: "I was in the water for 10 hours, so these wonderful guys rescued me". "I was sitting at the back of the deck", before she was led into an ambulance.
"The guest was found alive, is now in stable condition, and has been taken ashore in Croatia for further treatment", the company said in a statement. However, she still managed to explain that she was in the water for 10 hours.
"I am very lucky to be alive", she said.
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The rescue ship's captain, Lovro Oreskovic, said that she was exhausted.
A statement from the Norwegian Cruise Line said a guest fell overboard while the ship was on its way to Venice.
A year ago its report said: "Without exception, when investigations of MOB incidents are successfully concluded it is found that they were the result of an intentional or reckless act".
'We are very happy that the individual, who is a United Kingdom resident, is now safe and will soon be reunited with friends and family.
"We are pleased to advise that the guest was found alive, is now in stable condition", the cruise company said in an email to The Washington Post.
It was unclear how the woman went overboard.