A Chinese woman who was swept out to sea while swimming at a Japanese beach was rescued 37 hours later after drifting in a swimming ring more than 80 kilometers (50 miles) in the Pacific Ocean, officials said Thursday.

Japan's coast guard launched a search for the woman, identified only as a Chinese national in her 20s, after receiving a call Monday night from her friend saying she had disappeared while swimming at Shimoda, about 200 kilometers (125 miles) southwest of Tokyo.

The woman was spotted by a cargo ship early Wednesday, about 36 hours after she disappeared, off the southern tip of Boso Peninsula, the coast guard said.

The cargo ship 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.

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

The coast guard said she had drifted more than 80 kilometers (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.