Alan Wood, 49, originally from Brighton, was on a ferry with his wife Irenka and their three children after visiting the Parthenon earlier this month.
The family travel around the world in their boat and they were visiting the temple as part of their home schooling education for their children.
The vessel was sailing in the Saronic Gulf, which is between Athens and the island of Aegina.
Mr Wood and his wife, who are instructors at the Royal Yacht Association, instinctively shouted and pointed to alert the crew members and the captain.
He said: “If you see someone floating in the water, the standard procedure is yell and indicate where the person is.
“The captain then swung around and we got closer to the woman.
“She was miles off hore and she was not wearing a life jacket or anything to help her stay afloat.
“Nobody knew how she got there and it was a miracle we heard her screaming for help.”
Mr Wood’s video showed a lifebuoy was thrown towards the woman as passengers looked on.
One crew member then leapt off to pull the woman to one end of the vessel and managed to get her onboard.
The woman was pale and only able to communicate a little.
Mr Wood said: “The woman was stuck under the haul so someone had to get into the water to pull her out.
“She was exhausted but still conscious.
“Irenka is trained in CPR and she told the captain she was able to help the crew to ensure the woman was OK and was still breathing while the captain radioed for help.
“She was watching out for vital signs and to make sure she was not in shock.
“I am not sure if she was a local or a tourist. “We did our very best to help notify the crew members about the woman.
“As this is not our boat, and because of the language barrier, we were quite limited in what we could do to help.
“We’re very glad the woman is OK and that she is safe although it is still a bit of a mystery how she got there.
Click banner to register and browse
community posts by members