Directory of 5 Dive Sites or Spots for Scuba Diving in Tsushima and Iki Island, Japan

Tsushima Island and Iki Island are relatively new scuba diving destinations; official dive sites are few and the diving industry is in its infancy on the islands relative to the tropical Japanese islands to the far south such as Okinawa. Reportedly, the best shore diving off Tsushima is on Ohtahama Beach, off the town of Mitsushima. About 30 meters off the beach, there are four sided cement objects that have been placed as artificial reefs in 3-7 meters of water called tetrapods. This dive is good to get your fins wet and for beginners who want to dive off Tsushima.

The dive site known simply as Dokutsu (“cave” in Japanese) is the southernmost of the official dive sites in the area south of the town of Tsushima. The three cave entrances along the shore are half in water and perfect for beginner cave divers. You can get back in the cave enough to get into deep darkness, and the sunlight that shines in through the entrances is beautiful when making your way back out of the entrances. Another dive north of the caves is Kamabutase, a reef dive in a small bay where the reef goes down to about 25 meters. This is the richest dive site in eastern Tsushima for marine life. You can commonly see big, mature grouper and cardinal fish. When the current picks up schools of Japanese amberjack (also called yellowtail) spiral, making a show. The dive site is for intermediate dive skills due to currents. Another dive off the same eastern coast is a large flat reef area appropriate for all levels of divers known as Deka Matsu. The current is usually weak and allows you to explore the huge specimens of wire coral. The dive site's name itself means large “Deka”, wire coral “Matsu”. Young grouper live around the coral, as do schools of Pacific herring and bottom feeders fish known as Chicken grunt. The three mentioned dive sites: Dokutsu, Kamabutase and Deka Matsu are all accessible by boat from Takahama Gyoto, a small fishing port on Tsushima's east coast.

While 90% of the world's coral reefs are found in tropical waters, Tsushima reef is in relatively cold water. In fact, it is the coldest coral reef known on the planet. The reef lies out in the murky bay between Tsushima and Iki Island. Another cold-water reef closer to Iki Island was discovered in 2001, and until Tsushimi reef was discovered in 2012, the reef off Iki was the northernmost reef yet discovered. The newly found Tsushima reef is 70 km (43 miles) north of the Iki Island reef. The cold reefs are dominated by the massive brown coral genus Favia, found throughout the Indo-Pacific and Atlantic Ocean and known to thrive in colder waters. The more colorful, branching corals of the genus Acropora are not seen on this cold reef. Interestingly, Acropora have been anchoring and inching northward globally. The waters around Japan are apparently warming and Acropora is an indicator species used to detect warming trends.

Diving off Tsushima does not offer the clearest or warmest waters but it does offer a unique chance to see cold water reef and dive sites that have not been overly explored. There are many dive sites yet to be discovered and Tsushima would be an excellent place for advanced divers who want to dive uncharted territory scientifically and geographically.