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Yonaguni Island

From Openwaterpedia
Ryukyu Islands in southern Japan
Yonaguni Island diving spots
Yonaguni Island is famous as a breeding ground for hammerhead sharks that congregate around the island between November and May
Yonaguni Island is famous as a breeding ground for hammerhead sharks that congregate around the island between November and May
Steven Munatones completed a 29 km circumnavigation swim around Yonaguni Island in Okinawa in 7 hours 8 minutes in October 1994, televised on NHK-TV in Japan
Yonaguni Island in Okinawa, Japan

Yonaguni Island (Japanese: 与那国島 Yonaguni-jima) is one of the Yaeyama Islands and the westernmost inhabited island of Japan. It is the last of the Ryukyu Islands chain, and lies 108 kilometers (67 miles) from the east coast of Taiwan, between the East China Sea and the Pacific Ocean proper.


The island has an area of 28.88 km2 (11.15 sq miles), an annual mean air temperature of 23.9 °C, and annual precipitation of 3000 mm. All islands are under jurisdiction of the town of Yonaguni, Yaeyama Gun, Okinawa and there are three towns: Sonai, Kubura and Higawa. It was incorporated under the control of the Ryūkyū royal court in 1610.

Yonaguni, more specifically Cape Irizaki 24°26′58″N 122°56′01″E / 24.44944°N 122.93361°E / 24.44944; 122.93361 at the western tip of the island, is the westernmost point of Japan. Taiwan is be visible from Cape Irizaki on a clear day.


In the 12th century, it was incorporated to the Ryūkyū Kingdom. In the 17th century, it was incorporated into the Japanese han of Satsuma. By 1879, the island was formally incorporated into Japan. Until the early 20th century, Yonaguni was part of the larger Yaeyama village, which included the neighboring Yaeyama Islands. In 1948, it became an independent village. From 1945 to 1972, it was occupied by the United States and was then returned to Japan to form a part of Okinawa Prefecture.

Yonaguni is known in Japan for the hanazake, a 120-proof rice-based distilled beverage (awamori) produced only on the island. The island is also the only natural habitat of a distinctive horse breed, the Yonaguni horse. Yonaguni is a popular attraction for divers because of the large numbers of hammerhead sharks that gather in the surrounding waters during winter.

In the 1980s, local divers discovered a striking underwater rock formation off the southernmost point of the island. Yonaguni Monument has staircase-like terraces with flat sides and sharp corners (Yonaguni Monument).

This area is filled with sharks that can be easily seen from the surface of the water. Yonaguni Island is one of the world's most densely populated areas for hammerhead sharks.

Open Water Swimming

  • Water temperature was about 26.6°C where the first circumnavigation of the island was completed in October 1994 by Steven Munatones of U.S.A. in 7 hours 8 minutes.
  • Six Japanese men swam 95 miles (150 kilometers) from Yonaguni Island's Suao Harbor along the northeastern coast of Taiwan in an unprecedented cross-border swim in September 2011.

Japanese Atlantis

Diving among Hammerhead Sharks





国境の島であるため、台湾有事や尖閣諸島問題など周辺地域の有事に巻き込まれる蓋然性がある。2010年12月17日に閣議決定・公開された防衛計画の大綱及び中期防衛力整備計画 (2011)において200人規模の沿岸監視隊配備が盛り込まれ、平成23年度防衛予算では調査費として3000万円が計上された。これは中国の軍事的な脅威に対して、南西諸島に存在する警戒網の死角を埋める意味があり、同時に与那国の奇襲占領を抑止するためでもあるとされる。隊員の消費活動による、与那国町への経済波及効果も期待されている。






  • 最寒月平均気温18.2℃(1月)
  • 乾燥限界612mm<年平均降水量2363.5mm
  • 最少雨月降水量153.7mm(3月)






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