They are believed to be families who were fleeing the inferno - some were hugging when they were found.
About 300 firefighters and volunteers combed through the area looking for dozens still missing, who included 9-year-old twin sisters.
Mati, 29km east of Athens, is a popular spot for Greek holidaymakers, particularly pensioners and children at summer camps.
Hundreds of firefighters are battling the blazes and the authorities are seeking worldwide assistance.
"It's a hard night for Greece", Prime Minister Alexis Tsipras said after flying back to Athens from a trip to Bosnia that was cut short. It broke out in Mati late Monday afternoon and was still burning in some areas on Tuesday morning.
A fire brigade spokeswoman said at least 74 people were killed in the wildfires and the death toll was expected to rise. When they reached the beach and there was nowhere more to run, they swam into the sea, choking and blinded by the smoke and pulled by the strong current.
Video footage showed inhabitants fleeing the fires by vehicle, with several buildings and homes damaged, as the region of Attica - which includes Athens - declared a state of emergency.
At least 220 firefighters were on the scene there while five water-dropping planes and seven helicopters were fighting the blaze from the air.
"On behalf of the Filipino people and the Philippine Government, I would like to convey my deepest sympathies to the Greek people, especially to the grieving families of the victims and casualties of the catastrophic wildfire in Eastern Attica on 23 July 2018", Foreign Affairs Secretary Alan Peter Cayetano said in a statement on Wednesday.
Greece wildfires: At least 50 killed, over 150 hospitalised
"We mustn't let mourning overwhelm us, because these hours are hours of battle, unity, courage and above all solidarity", he said.
The coastguard said 19 people were found at sea and rescued while 696 people were picked up from beaches and the coastline by boat.
Over the two days, 47 brush and forest fires broke out across Greece, with a lot of them quickly extinguished, the fire department said.
More than 100 people have been injured in the fires raging on either side of Athens, charring farms and forests, and sending people racing to beaches to be evacuated by navy vessels, yachts and fishing boats.
Merchant Marine deputy minister Nektarios Santorinios, whose ministry is in charge of the coast guard, said more than 700 people had been evacuated by sea by the coast guard.
Responding to the appeal, Spain, Italy and Romania sent firefighting aircraft, while Cyprus sent in 60 firefighters. "By instinct I said to myself that this is it".
Reuters witnesses reported seeing a hillside of homes gutted by flames east of Athens.
Her sister had gone swimming, Saridou - who survived with light burns to her foot - said, but they became separated in the chaos of the fire.
Forest fires are common in Greece during the hot, dry summers, and temperatures recently hit highs up to 40 degrees Celsius.
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