The woman was reported to be swimming off Mahia Beach, near Gisborne on the eastern coast of New Zealand's North Island.
She was swimming with a male dolphin which has been a regular off the shore, attracting many swimmers into the sea.
On this occasion the dolphin, nicknamed Moko, would not let the woman swim to shore when she decided that she had had enough, barring her path shoreward. She was forced to cling to a buoy and shout for help.
Picked up by rescuers who came out in a rowing boat, she was reported by the Gisborne Herald to have been exhausted and very cold, even though she had been wearing a wetsuit to protect her from winter sea temperatures.
A possible explanation for the dolphin's behaviour, thought experts, was that fewer swimmers enter the water in winter, so that he gets lonelier.
Moko is the classic lone dolphin drawn to human company, having taken up residence off Mahia two years ago. He has scars from close run-ins with boats, and it is feared that it is only a matter of time before he is killed or very badly injured by such an encounter.
Most experts agree that wild dolphins – or even semi-tame ones, such as Moko – should be viewed from a distance, for the sakes of both the creatures and their human visitors.
On no account should they be chased or otherwise harassed by vessels, due to the risks of physical injury and mental anguish.
The UK-based Whale and Dolphin Conservation Society has formulated detailed policies on interaction with dolphins and other cetaceans in either the open sea or captive areas. To see its recommendations, click here.