Daigo Fukuryu Maru (第五福龍丸, Daigo Fukuryū Maru) was a Japanese tuna fishing boat, which was exposed to and contaminated by radiation caused by the United States' hydrogen bomb experiment in Bikini Atoll on March 1, 1954.

Kuboyama Aikichi, the boat's chief radioman, died a half year after the hydrogen bomb test on September 23, 1954, suffering from acute radiation sickness.

Before the incident

In 1947, it launched from Koza, Wakayama as a fishing boat named Dainana Kotoshiro Maru(第七事代丸, Kotoshiro Maru No.7). Later it became a tuna fishing boat in Yaizu, Shizuoka and was renamed the Daigo Fukuryu Maru.

Unexpected radioactive contamination

Daigo Fukuryu Maru encountered the American nuclear bomb experiment on Bikini Atoll, near the Marshall Islands, on March 1, 1954. The boat, along with its 23 boarding fishermen and fish, were contaminated by radiation. Then returned to Yaizu, Japan on September 14.

When the experiment was held, Daigo Fukuryu Maru caught fish out of the danger zone, which the U.S. government had declared in advance. The fishers realized danger and attempted to escape from the area, but they took time to retrieve ropes from the sea, causing them to be exposed radioactive fallout for a few hours. Later, the United States expanded the danger zone, and it was revealed many fishery boats were fishing at the time, besides Daigo Fukuryu Maru. It is estimated that about a hundred fishing boats were contaminated by radiation in experiment.

The tragedy of Daigo Fukuryu Maru brought rise to a fierce anti-nuclear movement in Japan. The U.S. government feared this movement would lead to an anti-American movement and attempted to expediently negociate with the Japanese government led by the prime minister Yoshida Shigeru, who was considered to be a pro-U.S. politician. The U.S. government paid $200,000 (USD) to the victims. The Japanese government also acknowledged that it would not pursue the further reparations from the U.S. government.

Daigo Fukuryu Maru is now on display in Tokyo.

Influence on popular culture

Five years after the accident, the Japanese film director Shindo Kaneto made a film titled Daigo Fukuryu Maru. The actor Uno Jukichi played the role of Kuboyama Aikichi.

This incident further inspired other movies such as Godzilla, which told the story of a monster mutated from radioation seeking revenge against civilization.