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Chapter Twenty-Seven
Confronting Yonaguni

The One Archaeologist

One archaeologist has dived at Yonaguni and studied its underwater structures first hand. Others in his profession who have commented have done so from their desks after browsing through photographs or looking at videotape of the structures. As is the case with the armchair geologists, their opinions can only be of limited value until they have dived there themselves.

By contrast the opinion of the only experienced marine archaeologist in the world who has ever dived at Yonaguni must count for a great deal more.

That archaeologist -- whose official report is reproduced in part below -- is Sundaresh from the National Institute of Oceanography in Goa, India. The reader will recall that we dived with him and other NIO archaeologists at Dwarka in March 2000 and again at Pumpuhar in February 2001. Between these expeditions in India, Sundaresh participated with us in an expedition to Yonaguni in September 2000 that had been sponsored once again (as had Robert Schoch’s visit in September 1997) by Seamen’s Club.

Also participating in the September 2000 expedition was Kimiya Homma, a businessman from Hokkaido, whose firm owns two very useful high-tech ROVs (remotely operated vehicles) for unmanned exploration in water too deep to be readily reached by divers. So that an effective search for further structures around Yonaguni could be mounted in the short time available, Homma had brought one of the ROV’s with him and also an expert team of support staff and technical divers.

Because it is a unique document of reference, being – so far – the first and only evaluation of a wide range of Yonaguni’s underwater structures by a marine archaeologist, I reproduce below several sections from Sundaresh’s expedition report. Some of the specific submerged sites that we visited with Sundaresh during the expedition are not yet familiar to the reader from the brief account given in Chapters 1 and 25 but will be described shortly:


1-12 September 2000


Yonaguni is the most south western island of Japan and closest to Taiwan (about 69 nautical miles). This island is almond shaped with 10 km length from (east to west) and 4 km width (north to south). An international expedition was organized by the Seamen's Club, Ishigaki Japan to further explore the underwater structures in the area. This report describes the archaeological significance of the structures found during the expedition.


Underwater massive structures were found initially by Mr. Aratake a local resident of Yonaguni island during 1986-87. He named this point as Iseki (“Monument”) Point. He was looking for hammerhead sharks schooling around the island, when a massive man-made underwater structure was noticed at a depth of 30 m. This was his first discovery. Later more monuments were found by Aratake and other divers in nearby Tatigami and “Palace” areas.


4.1 Offshore Explorations

Two boats were chartered for explorations off Yonaguni waters from 2 September 2000 to 8 September 2000. The Remotely Operated Vehicle (ROV) was deployed simultaneously with side scan sonar and echosounder. The ROV was operated with generator power supply. The system was operated in waters between 40 to 80 metres depth around Yonaguni. The survey revealed rock cut channel about 1 m wide and more than 20 m long at 2 sea mounts. The ROV observations were confirmed by diving.


5.1 Terraced Structure and Canal

A large terraced structure of about 250 metres long and 25 metres height was studied south of the Arakawabana headland. Known locally as Iseki Point, the terraced structure is bound to the northern side of an elongated, approximately east-west trending structure, designated by Professor Masaaki Kimura, University of the Ryukyus, as an approach road. But our observation of the proposed road-like structure suggests that it is more likely to be a canal. The overall width of the terraced structure is around 100m. From each of the terraces; a staircase leads downwards to the canal(road ?).

The length of the canal appears to be more than 250 m, while the canal has a width of 25 m. The purpose or utility of this canal structure is intriguing. Our observation all along the canal indicates that, the western end of the structure begins underwater opening away from the terraced structure into the open sea. The width, height and terraced northern side of the canal force us to suggest that the canal structure might have served as a channel for small boats communicating with the Arakawabana headland. The southern natural outcrop wall probably had provided a buffer wall for strong open sea waves. This interpretation appears quite reasonable because the height of the southern wall of natural outcrop and the northern terraced wall are nearly same. The terraces and attached staircases might have been used for handling, loading and unloading boats sailing through the channel. Thus it appears in all probability that the terraced structure and canal might have served as a jetty before submergence to present depth.

5.2 Monolith Human Head

A large monolith that looks like a human head with two eyes and a mouth was studied at Tatigami Iwa Point. A human-cut large platform in the same monolith extends outwards at the base of the head. An approach way leads to this platform from the shore-side.

The surrounding basal platform is quite large (about 2500m2 ), and could easily have accommodated more than two thousand persons sitting. The human head and associated platform with an approach road are suggestive of an area of worship or community gatherings.

5.3 Underwater Cave Area

Diving operations revealed caves at 8 to 10 m water depth at “Palace” area. The entry to these caves was possible only through the large 1 metre radius holes on the cave roof. Inside the cave a boulder about 1 metre diameter engraved with carvings was observed. About 100 m towards the eastern side of the caves more rock engravings were noticed on the bedrock. These rock engravings are believed to be man-made.

Once upon a time these caves were probably on the land and were later submerged. The rock engravings inside the cave and on the bedrock were probably carved out by means of a tool of some sort. However, it is very difficult to say that these are rock art of this or that period, or a script.

5.4 Megaliths Point

Diving operations revealed two big rectangular blocks measuring 6 metres in height, about 2.5 metres in width (both) and 4.9 metres thickness which have been located towards the western side of Iseki point... These rectangular blocks are designated by Japanese workers as megaliths. These blocks have been located in between two natural rock outcrops. The approach way to these megaliths is through a tunnel measuring about 3 m long, 1 m high and 1 m width.

The shape, size and positioning of these megaliths suggest that they are man-made. It is believed that the people of Japan’s extremely ancient Jomon culture used to worship stones, rocks, (Hancock, personal communication, 2000). In light of this practice, it may be worthwhile to suggest that, these megaliths might have been used as objects of worship. However a thorough investigation in this regard is necessary before assigning a definite purpose to these megaliths.


The terraced structures with a canal are undoubtedly man-made, built by cutting an existing huge monolithic outcrop. The rectangular terraced structure and canal probably might have served as a jetty for handling, loading/unloading small boats before its submergence to present depth.

The monolith rock-cut human head and associated platform might have served as an area of worshiping or community gatherings.

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