Joint Chiefs of Staff said Friday the boat was found some 30 meters off the coast of Goseong, Gangwon Province. The town is situated about 20 kilometers away from the border with the North.
They also noted that nobody was aboard the boat at the time of the discovery.
Authorities said while circumstances do not seem to merit suspicion of espionage, an investigation is underway for further confirmation.
This is the second instance of a North Korean boat discovery in South Korean waters in less than a month.
On June 15, a North Korean fishing boat with four North Korean men aboard docked at the eastern port of Samcheok, Gangwon Province. The boat crossed the maritime border and navigated through South Korean waters undetected for about 57 hours.
By Kim Arin (email@example.com)