SEOUL, Aug 7, 2025 (BSS/AFP) - A North Korean defector who swam across a sea border with South Korea while reportedly tied to floating plastic has been rescued and taken into custody, Seoul authorities said Thursday.

The North Korean managed to swim across the de facto maritime border off the western coast of the Korean peninsula on the night of July 30, South Korea's Joint Chiefs of Staff said.

The border is known as the Northern Limit Line and has occasionally served as a route for North Korean defectors swimming to South Korea's Ganghwa Island.

"The military identified the individual near the north of the mid-river boundary," a military official told reporters.

The individual, who local media reported was tied to Styrofoam when he was found, waved for help and said he wanted to defect to South Korea when asked by a South Korean naval officer, the official said.

The operation took about 10 hours, according to Seoul, and the individual was rescued at around 4:00 am on July 31 (1900 GMT July 30).

The North Korean is now in custody and has expressed their wish to defect, the defence ministry said.

Ganghwa Island, located northwest of Seoul, is one of the closest South Korean territories to North Korea, with some parts of the surrounding sea lying just 10 kilometres (six miles) from the maritime border between the two countries.

Tens of thousands of North Koreans have fled to the South since the peninsula was divided by war in the 1950s, with most going overland to neighbouring China first, then entering a third country such as Thailand before finally making it to the South.

Defections across the land border that divides the peninsula are relatively rare, as the area is densely forested, heavily mined and monitored by soldiers on both sides.

But a North Korean man defected last month to the South by crossing the Military Demarcation Line.

The number of successful escapes dropped significantly from 2020 after the North sealed its borders -- purportedly with shoot-on-sight orders along the frontier with China -- to prevent the spread of Covid-19.

North Koreans are typically handed over to Seoul's intelligence agency for screening when they arrive in the South.