The 7m boat was found in Akita Prefecture in northern Japan, according to Kyodo News, after a 68-year-old woman notified authorities about a dilapidated, drifting vessel.
"I was surprised to see the boat in such a bad condition," she told the news organisation.
Later, she said, she watched as authorities used stretchers to carry bodies off the boat.
About 1000 people successfully defect from North Korea each year, and about 30,000 have fled to South Korea since the end of the Korean War in 1953. They tell stories of sometimes violent reprisals for political speech, being banished to labour camps for watching American movies, and old-fashioned starvation.
But a silent, unknown number never survive the escape attempts, dying during desperate journeys to South Korea or China or Japan.
Others are captured and face severe punishment for trying to leave.
According to Vice, "the North Korean penal code states that defectors face two years of hard labour if they are caught crossing the border," though punishments can vary.
Radio Free Asia reported that North Korean officials warned that citizens living near the Chinese border who are caught helping people defect would be put to death — and the punishments wouldn't stop there. Family members of violators can be imprisoned or banished to remote regions of North Korea.
Still, North Koreans defect by the hundreds. This month, the world was riveted by the story of a North Korean soldier who escaped in dramatic fashion a few weeks ago — driving a Jeep southward until it got stuck in a ditch, then sprinting across the demilitarised zone.
His former comrades shot at him with pistols and assault rifles, putting at least five bullets into him.
South Korean soldiers found him in a pile of leaves and dragged him to safety, and he was flown to a hospital via helicopter.
Even before they learned his name, doctors said his condition told some of his story, according to the Washington Post's Marwa Eltagouri. He had hepatitis B and tuberculosis, and parasitic worms nearly 30cm long in his intestines.
Doctors say the worms point to the health and humanitarian crises inside the closed borders of North Korea.
Since then he has been recovering — and has become a source of demilitarised zone trolling.
South Korean soldiers have been broadcasting details about the defector's improving medical condition across the demilitarised zone, according to Newsweek.
The speakers they use, which at one point were used to encourage soldiers to defect, can apparently be heard more than a dozen kilometres away.
"The news about an elite soldier like a JSA guard having fled in a hail of bullets will have a significant psychological impact on North Korean border guards," said a military spokesman quoted in the South Korean newspaper Chosun Ilbo.
