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Yonaguni Island

24°27'N 122°59'E
Yonaguni Map Diving Yonaguni Ruins
Click above map to show all main dive sites in Japan

Yonaguni Overview

The sub-tropical island of Yonaguni is a little rugged island 67 miles off the coast of Taiwan and a 30 minute flight from Ishigaki. This 15sq mile island isn’t the most attractive in the Yaeyama chain but does have a feeling of remoteness being so far from mainland Japan. There is one big reason for heading to Yonaguni as a diver – an ancient and mysterious underwater monument.  The ‘Iseki’ were discovered in the 1980’s by local diver Kihachiro Aratake san and are thought to be an ancient monument modified by man in the last ice-age around 10,000years ago. If they are manmade, the stones would be the oldest manmade monument on earth predating the Egyptian Pyramids.

Below is a 10 minute documentary in English about Yonaguni and the diving to see the monument.

The Iseki consists of several monuments with the main terrace area consisting of a single platform 100 metres by 50 metres and more than 25 metres tall. The structure is seemingly carved out of rock and consists of perfect right angles, huge steps and deep corridors. There is debate between those that believe that it is an ancient manmade structure and those that believe that it is merely a geological phenomenon continues. There are also those that the stones are an extension of the lost continent of Mu and those that believe that this is the work of aliens. Either way, this dive site is truly stunning for the most experienced diver.

Away from the stones, the waters are great for diving. The visibility is crystal clear most of the year round and there is a lot of drift diving opportunity with strong currents that surround the islands. Between November and June is considered Hammerhead season with the winter months producing breathtaking scenes of schooling Hammerhead sharks with the creatures spotted on a daily basis. There are plenty of beautiful coral, interesting rock formations and an abundance of sub tropical marine life around the islands to make Yonaguni the best kept diving secret in the world.


There are approximately 70 dive sites around Yonaguni, but the main attraction to the area are the mysterious stones.

The Yongauni Iseki stones can be dived all year round and start at 10 metres.

Other highlights

Hammer Head Rock - 20m
One of the best spots for shark and Hammerhead in particular.

Double Arch  -  24m
Beautiful coral formations

"Great hole"  - 18m
 A limestone cave formation under water.

Diagram of Yonaguni Ruins
Map courtesy of


Seasons - facts and Figures

Jan - Mar)

Air temp:


Water temp:


Wet Suit:

5mm three piece or one piece


Squid, Whale Shark, Giant Trevally ( best from March), Schooling Hammerheads, Dogtooth Tuna, Bigeye Trevally, Turtle, Barracuda, Eagle Ray

Apr – May

Air temp:


Water temp:


Wet Suit:

5mm one piece


Squid (to end April), Marlin, Whale Shark, Giant Trevally, Schooling Hammerheads, Dogtooth Tuna, Bigeye Trevally, Turtle, Barracuda, Eagle Ray

Jun – Sep

Air temp:


Water temp:


Wet Suit:

3mm one piece


Dogtooth Tuna, Bigeye Trevally, Turtle, Barracuda, Eagle Ray, Giant Trevally

Oct – Dec

Air temp:


Water temp:


Wet Suit:

5mm one piece or suit


Squid (from December), Schooling Hammerheads (from Nov),
Dogtooth Tuna, Bigeye Trevally, Turtle, Barracuda, Eagle Ray, Giant Trevally
NB: Temperatures rarely dip below 20C in Ishigaki, but there is a brief rainy season from mid-May to early June which may see short rain showers during these months.

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