A 21-year-old Chinese woman who was reported missing has been rescued from the open sea near Tokyo after drifting over 36 hours.

She was found and rescued from the sea off Chiba Prefecture near Tokyo, Kyodo News reported, citing a local coast guard office.

The woman was swimming with a friend during their travels at Shirahama Ohama beach in Shizuoka Prefecture, at around 7:30pm on Monday (Jul. 8).

The beach is about a three-hour drive away from Tokyo.

She was later reported missing to the police.

When she was found, she had drifted over 80 kilometres.

The woman, who was on a swim ring, was dehydrated but conscious.

Airlifted to a hospital

She was airlifted by a Coast Guard helicopter and transported to a hospital in Yokohama, according to NHK.

The woman later told officials that she realised she was drifting about 30 minutes after she began swimming.

She attempted to return to the beach but failed to do so.

Moderately strong winds of about 36 kilometres per hour were blowing at the time of the incident, according to rescuers.

Officials believe she was swept away by the currents and winds.

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Top image via Shimoda Tourist Association.