Updated

A woman who was swept more than 50 miles out to sea while swimming at a Japanese beach has miraculously survived after spending 37 hours in the water, officials say. 

A cargo ship spotted the woman, identified only as a Chinese national in her 20s, drifting in a swimming ring early Wednesday off the southern tip of the Boso Peninsula, according to Japan’s Coast Guard. 

She vanished while swimming at Shirahama Ohama beach in Shimoda, about 125 miles southwest of Tokyo, the AFP reports. 

"It was around 7.55pm on July 8 when we received the information after the woman’s friend reported to a nearby convenience store that she was missing," a local Coast Guard official told the news agency. 

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Woman is airlifted by a coast guard helicopter

A woman is airlifted by a coast guard helicopter off Nojimazaki in Japan's Chiba prefecture on July 10. The woman, who was swept out to sea while swimming at a Japanese beach, was rescued 37 hours later after drifting in a swimming ring 50 miles away in the Pacific Ocean, officials said on Thursday. (Japan Coast Guard via AP)

The cargo ship that spotted the woman asked a passing LPG tanker, the Kakuwa Maru No. 8, to help. Two of its crew members jumped into the sea and rescued the woman, officials said. She was airlifted by a coast guard helicopter to land, they said. 

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Shirahama Ohama beach

Shirahama Ohama beach in Japan, where the woman vanished from before being rescued at sea.

The woman was slightly dehydrated but was in good health and walked away after being examined at a nearby hospital, the officials said. 

Beach in Shimoda, Japan

One of the many beaches in Shimoda, Japan, which is about about 125 miles southwest of Tokyo. (Google Maps)

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The coast guard said she had drifted more than 50 miles and was lucky to have survived despite the dangers of heat stroke under the sun, hypothermia at night or being hit by a ship in the dark. 

The Associated Press contributed to this report.