A Hoverspeed cross-Channel ferry went to the aid of a yacht on Sunday night after it sent out a mayday call reporting that the vessel was sinking.
The British yachtsman on board the 47ft Zaramanda told Dover Coastguard the craft was taking on water but it later emerged that his wife was ill.
The woman - who was suffering extreme seasickness - was taken to Newhaven, East Sussex, by the French coastguard.
A spokesman for Dover Coastguard said an inquiry would be carried out.
"The ferry was full of passengers and was alongside for more than 40 minutes," he said.
"It was a strange incident - we were told the ferry was taking on water but that appears not to have been the case."
The Zaramanda, which had been midway across the Channel, was escorted to the East Sussex port of Newhaven by tug after the woman was winched onto the French coastguard helicopter in strong winds.