The four of them had taken a boat and gone for a swim at Saint Nikolas Beach – however, Dr Mosley preferred to return on foot at around 1.30pm, Athens-based newspaper Kathimerini reported.
The CCTV images were captured by a restaurant at around 2pm local time, police believe.
The beachside eatery is located in the Pedi area of the island, a small town in a bay around 1.2km from Saint Nikolas Beach.
The images appear to show the 67-year-old wearing a dark t-shirt, shorts and a cap. He is carrying an umbrella.
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Dr Mosley, his wife and the other couple arrived in Symi for a week’s holiday on Tuesday, according to local media.
The doctor had been missing for just over 48 hours, as of Friday afternoon.
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Symi has been experiencing hot temperatures this week and its mayor Lefteris Papakalodoukas told a local news site the heat on Wednesday was “unbearable and one could easily faint in such conditions”.
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The rescue operation has been focusing on the Pedi area after a woman reported seeing him there on Wednesday.
The extensive search has so far seen five coastguard patrol boats deployed while private and commercial vessels in the area have also helped.
Police and firefighters have used drones to scan the island and a helicopter was deployed at around 7pm local time on Thursday. Sniffer dogs have also been used in the search.
Divers have been looking in the water, Symi deputy mayor Ilias Chaskas previously said.
Authorities have considered a number of possibilities, including Dr Mosley may have suffered a fall – or could have been bitten by a snake, Greek news website ekathimerini.com reported.
One woman in the Pedi area said the TV doctor’s disappearance was “strange” as the path he was thought to be on is “clear”.
“It’s a quiet place,” she said. “If you see the map of the area it’s a clear path, it’s nothing dangerous.
“Many people go every day, every few minutes, that’s the reason it’s very strange because it’s a clear path.”
Dr Mosley is a columnist and broadcaster who has made a number of films about diet and exercise.
He fronted the Channel 4 show Michael Mosley: Who Made Britain Fat? and was part of the BBC series Trust Me, I’m A Doctor. He has also appeared on numerous daytime television shows.