Scuba diving is without a doubt the main draw for most visitors to Yonaguni. However, the island's location in the middle of the open sea without protective reefs means that waves can be high and currents can be strong, so most diving here is drift diving and many of the more interesting dive sites are only accessible to experienced divers.
Open Coast Travel
Los angles, ca, tel. 1-310-433-6653, (http://www.opencoastravel.com). open coast travel is the only us based travel agency specializing in guided scuba tours to yonaguni for western travelers. all bilingual guides have lived in japan.
Yonaguni Diving Service
Kubura, tel. 0980-87-2658, (http://www.yonaguniyds.com/). the oldest and largest dive shop on the island, quite professionally run: they will cater to your experience level and will not head out to sites if the weather does not permit in which case your money is refunded. two boat dives start from ¥12,000, full gear rental for a day is ¥6,500. no credit cards accepted and only limited english spoken. quite popular, so book ahead.
sharks
In addition to the ruins, Yonaguni is also famous among Japanese divers for its hammerhead sharks, which congregate around the island and can be spotted on most dives in the cooler winter season December-February. Yonaguni is also pretty much the only spot in Japan where it is possible to spot the giant whale shark, the largest of them all, although sightings are quite rare.
underwater ruins
Yonaguni's unique attraction for archaeologists and divers alike are the mysterious underwater ruins æµ·åºéºè·¡ kaitei iseki which lie off the southern coast of the island. A single platform 100 by 50 meters wide and up to 25 meters tall, seeming carved out of solid rock at perfectly right angles and dated by some to be 8000 years old, the technology required to build them here doesn't seem to match any known timeline of human history. Some maintain that they are the product of the lost Continent of Mu or even alien artifacts, while the most boring explanation would be that they are merely the product of strange geological processes — although the apparent hallways and staircases, as well as what appear to be regular rows of holes dug for moving rock and even what some take to be a form of writing on the walls, would appear to defy this.
Seeing the ruins, however, takes some time, effort and skill: the area is notorious for its currents and not suitable for beginning divers, although several diving shops run one-day crash courses that culminate in a guided tour of the ruins. For those with the requisite skills PADI AOWD or more, a day's diving starts at ¥12,000. Note that the ruins, some 20 minutes by boat from Kubura, are usually only accessible when they are on the leeward side of a north wind and the currents are not too strong, so you'll also need some luck just to get here.
Wind conditions permitting, SOUWES diving service can also arrange glass-bottomed boats to make the trip for ¥5000/head if there are five or more passengers or you can charter the whole boat yourself. Don't expect to see very much, as the ruins are at a depth of 5 to 20 meters, when the weather is bad.
caverns
Much of the southern coastline is dotted with caverns, caves and underwater rock formations, which make for spectacular but, again, slightly challenging diving. Daiyati and the Temple of Light are particularly well-known spots that bear more than slight resemblance to Swiss cheese.
Other
Other events of note on Yonaguni include:
Swordfish Fishing Competition
ã«ã¸ãé£ãå¤§ä¼ kajiki-tsuri taikai, (http://www.town.yonaguni....). yearly in july.