KANTŌ
The Kantō region, on the main island of Honshū, is Japan’s most populated area, due to the sprawling Tōkyō Metropolis, and yet this section of Pacific coastline offers amazing diving, with the chance to see both world-class macro, but also schooling hammerheads, dolphins and more.
Just make sure to avoid Japanese holidays and weekends as much as possible to stay away from crowds and queues, especially on dive sites easily accessible from Tōkyō, which can get very busy.
The Kantō region can be divided into two main diving areas:
- the Pacific coast area of main island of Honshū and the neighbouring islands
- The more remote islands of the Nanpō archipelago, spreading south of the Izu Peninsula.
Kantō’s Tōkyō Metropolis administers all the Nanpō islands (primarily the Izu and Ogasawara/Bonin island chains), which stretch over 1000 km to the south of the Honshū’s mainland into the Philippine Sea, offering increasingly subtropical conditions as you go further south.
The Nanpō islands offer a unique environment, unlike what you would find elsewhere in Japan due to the island chain’s geographical position, with stunning volcanic topography and many endemic species that developed there, in relative isolation.
The Nanpō archipelago starts, off the coast of the Izu Peninsula, with the 7 main Izu Islands, that offer great diving (and famous sites such as Nazumado, Akinohama, and Keikai) and are reachable by ferry or plane (Izu Ōshima and Hachijō-jima have airports), and continues down south, with generally warm water and increasingly subtropical conditions, all the way to the Ogasawara/Bonin Islands, reachable only by a 26 hour+ ferry ride from Tōkyō (no airport…)
The Ogasawara islands are sometimes nicknamed the “Galapagos of Japan/the Orient”, which might be pushing it a little, yet the logic behind this nickname is that these islands, like the Galapagos, were never actually connected to any continental landmass, meaning that their animal, plant and marine life all evolved independently, resulting in a large number of endemic species.
As a side note, Iriomote Island (Yaeyama Islands, Okinawa Pref.), is also sometimes nicknamed the Japanese Galapagos, because it is still a rather wild area, so do take such alluring nicknames with a pinch of salt…
In our opinion, the Izu islands do however share many common features with the equally volcanic and isolated Macaronesian archipelago (made up of the Azores, Madeira, Canary and Cape Verde Islands and mainly administered by Portugal and Spain), which are also great diving destinations found off the coast of West Africa, in the Atlantic Ocean –
the “Azores of Japan”®, anyone? 😉 You read it here first!
The islands of the Nanpō chain offer great diving and topography, endemic species (like Hachijō-jima and Ogasawara’s emblematic Yūzen/wrought-iron butterflyfish (Chaetodon daedalma) and complex conditions linked to the area’s exposure to warm and cold water currents.
The whole Kantō area, including the Izu islands, is strongly affected by the Kuroshio warm current, and features strong seasonal changes in water temperatures and species.
MAIN DIVING AREAS MENTIONED
Pacific Coast of Honshū
- Tōkyō Bay (Tōkyō Metropolis)
- Kanagawa Prefecture
- Chiba Prefecture
Nanpō Archipelago
- Izu Islands (Tōkyō Metropolis)
– Izu Ōshima
– Shikine-jima
– Kōzu-shima
– Miyake and Mikura-jima
– Hachijō-jima - Ogasawara/Bonin Islands (Tōkyō Metropolis)
– Chichi-jima
DIVING HIGHLIGHTS AND ICONIC MARINE LIFE
CORAL REEFS, BLUE WATER AND VISIBILITY
The islands of the Nanpō archipelago offer the chance to dive on healthy hard and soft coral reefs.
The waters of the Izu and Ogasawara islands are particularly famous for their blue colours (“Hachijō Blue”, “Bonin Blue”) and great seasonal visibility.
WRECK DIVING
The Chichi-jima area in the Ogasawara/Bonin Islands has numerous WWII wrecks, including the Daibi-Maru (sometimes recorded as Daimi-Maru), lying at 33 m depth in Chichi-jima harbour.
These wrecks are not all easily accessible, and some require special equipment and adequate training, and authorisations, so do your research.
Some beautiful pictures of the wreacks of the Ogasawara islands area can be found here.
ICONIC SPECIES
There are many local endemic/iconic species, including schools of wrought-iron butterflyfish (Chaetodon daedalma) and red tail triggerfish (Xanthichthys mento) found in the Nanpō archipelago’s Izu and Ogasawara islands.
Sand tiger sharks / ragged-tooth sand sharks “raggies” (Carcharias taurus) are found all year round in the Ogasawara Islands.
MACRO DIVING, ODD AND RARE CRITTERS
The Kantō region offers great macro diving, where you dive to spot/photograph/film small rare critters.
Sites like Jogashima or Hayama in Kanagawa Prefecture, Tōkyō Bay and in the Nanpō islands offer a world class seletion of nudibranchs (sea-slugs).
There are many rare nudis to be found, and also less rare but still highly popular/photogenic specimens such as the “Pikachu”or the “Shaun The Sheep” nudibranchs.
Tōkyō bay (Tōkyō Metropolis) is said to have really amazing nudibranchs (sea slugs), possibly because of the heavy maritime traffic in the port area, and the ballast waters the ships carry for vessel stabilisation.
Ballast waters are said, for instance, to be largely responsible for the lionfish crisis in Caribbean waters, where this imported species found no local predators and proliferated.
The same could be true, with less dire consequences, for the Tōkyō Bay area’s outstanding nudibranchs population.
Another solid theory is that great macro diving sites like Jogashima (Kanagawa Pref.) are located at a topographic intersection of bays (Tōkyō, Sagami) and the Kuroshio current, leading to complex interactions and species mobility.
The Nanpō Archipelago’s Izu Islands, especially Izu Ōshima, Hachijō-jima and Kōzu-shima, are famous in Japan for their rich macro-life, rare nudibranchs and all the usual suspects but also the famous Japanese pigmy seahorse (Hippocampus japapigu), along with more classic pigmy seahorses (Hippocampus bargibanti,. h. colemani and h. pontohi), often spotted on the Izu and also in the Ogasawara Islands (Tōkyō Pref.).
Larger species of seahorses are also common, including the crowned seahorse (Hippocampus coronatus), endemic to the Japan’s Pacific coastal waters and mostly found in Zostera seagrass.
Other macro highlights include:
Various pipefish, including ornate and robust ghost pipefish (Solenostomus paradoxus and S. cyanopterus)
Crabs, including spider crabs, decorator crabs
Lumpfish like the odd-looking Lethotremus awae, seen in winter at Iwa or Enoshima in Kanagawa Pref., a real favourite of Japanese divers.
Rare and odd-looking frogfish/anglerfish (Antennariidae), especially in Ishibashi or Hayama (Kanagawa Pref.)
Shrimps, including the highly photogenic harlequin shrimp (Hymenocera picta) and imperial shrimp (Periclemenes imperator) or skeleton shrimps
Rare, singular jellyfish and anemones
Rhinopias, leaf scorpion fish (Taenianotus triacanthus), seamoths (Pegasidae), devilfish (Inimicus) and other weird, photogenic critters
Rare blennies and gobies
Tōkyō Bay (Miura peninsula, Kanagawa Pref.) offers proper muck diving as well, with both silty and sandy areas.
SCHOOLING HAMMERHEAD SHARKS
The Kantō region offers the possibility of diving with scalloped hammerhead sharks (Sphyrna lewini) in the Izu islands.
While this is definitely less famous, and more adventurous Japan’s famous hammerhead viewing sites of Izu’s Mikomoto islets or Okinawa’s Yonaguni island, Izu Ōshima Island is only a 2-hour fast-ferry ride or a 40 min flight away from Tōkyō.
In the summer months, lucky divers can observe schools of scalloped hammerhead (Sphyrna lewini) on a very early morning beach entry dive (!!!) at Keikai, which is quite a unique experience.
You do have to get up at 4 am, and it is an advanced dive, quite shallow but with strong current, where you hold on to rock and watch the action go by.
On a good day, you might get to see what people call the “hammer river”, a long stream of hammerheads flowing by in the current…
Best period to view the hammerheads is said to be between mid-June and October.
DOLPHINS
Swimming and freediving/snorkeling with pods of wild bottlenose dolphins (Tursiop aduncus) is one of the highlights of the Nanpō islands, both in the Izu and Ogasawara island groups.
In the Izu island, the hub is Miyake-jima, from which a one-hour boat trip takes you Mikura-jima, where it is possible to join the 3 or 4 boat trips per day organised to snorkel/freedive with the island’s resident pods of 200+ wild (non-captive) bottlenose dolphins, who often come up to swimmers and snorkelers and play around them.
The Miyake branch of the Dolphin Communication Project tracks the pods of dolphins that live around the island.
Dolphins are sometimes also seen on dive sites of other Izu islands.
The Ogasawara/Bonin Islands also offer many great opportunities freedive /snorkel with wild dolphins and other cetaceans, and they are very frequently spotted by scuba divers on local dive sites.
TURTLES
Shikine-jima, Hachijō-jima and the other Izu islands are all famous for their “sea” turtle populations, including green and hawksbill turtles (Chelonia mydas and Eretmochelys imbricata)
Shikine-jima also has a spot where turtles like to relax in warmth of the hot springs that flow into the sea, a kind of reptilian alternative to Nagano’s bathing “snow monkey”, if you wish…
From February to August the Ogasawara/Bonin Islands are said to become one of the biggest nesting ground of green turtles in Japan.
WHALES
Humpback whales (Megaptera novaeangliae) are spotted, mostly from the boat or shore but quite regularly underwater in the winter to spring months, in the Ogasawara/Bonin Islands (usually between February and April), and also around the Izu Islands in the winter months (December to March).
Keep in mind that unless you encounter a whale while already in the water, interaction with the whales is not allowed in the Ogasawara islands, as boats are required to respect a 100 m exclusion zone around humpback whales.
Sperm whales (Physeter macrocephalus) are also common in the Ogasawara islands during the summer to autumn months, and the islands are one of Japan’s best whale watching / spotting destinations along with the north of the Okinawa island chain.
A 50 m exclusion zone is to be respected around sperm whales, again, unless you are already in the water and the whale comes up to you.
Seasonal whale watching in the Izu islands (such as Hachijō, where whales can sometimes be seen from some of the island’s outdoor hot springs / rotenburo) is still developing as an activity, so expect to hear more on that in the future.
Mola Mola
Common mola / sunfish (Mola mola) can be observed seasonally on special dives organised seasonally in Ito-Tateyama (Chiba Pref.)
SCHOOLING FISH, PELAGICS AND PREDATORS
Large schools migratory fish and pelagics, including dogtooth tuna (Gymnosarda unicolor), bluefin trevally (Caranx melampygus), big-eye trevallies great amberjacks (Seriola dumerili) Japanese amberjack (Seriola quinqueradiata) and rainbow runners (Elagatis bipinnulata) and various types of larger pelagic sharks can be seen seasonally in the Kantō area.
This is especially true in the more remote islands of the Nanpō archipelago, from Hachijō-jima in the Izu Islands to the Ogasawara Islands.
The Ogasawara islands are famous for their massive schools of dogtooth tuna (Gymnosarda unicolor), Japanese Spanish mackerel (Scomberomorus niphonius) greater amberjacks (Seriola dumerili), trevallies or barracudas.
Pelagic thresher sharks (Alopias pelagicus), whale sharks (Rhincodon typus) and scalloped hammerhead sharks are sometimes spotted at different sites in the Nanpō islands, due to the combined effects of currents, relative isolation and deep water.
Smaller sharks such as sleeping white-tip reef sharks (Triaenodon obesus) in winter months at Kamogawa (Chiba Pref.), various rays including guitar-sharks/shovelnose rays (Glaucostegus typus) or Japanese bullhead sharks (Heterodontus japonicus) are spotted in most of the area, including the Izu Islands.
Schools of Japanese eagle rays (Myliobatis tobijei) can sometimes be seen in the summer months at Nishikawana (Chiba Pref)
Though rare, manta rays, mostly giant “oceanic” manta rays (Mobula birostris) are regularly spotted in the Ogasawara islands area (see here for more info on the subject)
SPAWNING EVENTS AND AGGREGATIONS
Japanese flying squid (Todarodes pacificus) spawning events can be observed in May in Miyake-jima in the Izu Islands,, as squid brought by the Kuroshio current congregate and spawn in the area.
The squids deposit long white tubes full of eggs in clusters on tree branches placed there by dive operators, at about 14-16m depth, on shore dive from Okubohama beach.
BANDED HOUND-SHARK AND RED STINGRAYS FEEDING DIVE
Dives involving feeding and or baiting/chumming are quite controversial, especially in contexts located outside North-American influence.
The overall impact of such practices is debated – even though the commercial value of shark-encounter operations where sharks are baited/fed for divers’ enjoyment such as those found in the Bahamas, Fiji, Mexico’s Guadalupe or in the Azores is obvious.
Proponents argue that this actually helps conservation efforts and does not affect the local ecology and marine life behaviour.
Japan offers one such dive, in Tateyama-Ito (Chiba Pref.), called the “Shark Scramble” (or “Shark City”) where it possible to dive with hundreds banded hound-sharks (Triakis scyllium) and red stingrays (Hemitrygon akajei) during a frantic feeding/chumming session.
The story behind this dive it is that its creator, Mr Kan Shiota, successfully turned animals that local fishermen were treating as pests (since they were getting caught in nets) into a lucrative tourist attraction by gradually luring them to one dedicated area, where divers feed them twice a day.
This was done in collaboration with local fisheries and legally, since local accreditation to do so was granted, and is presented as a part of a conservation effort, to keep the sharks out of the nets of the fishermen.
The feeding session also attracts other large stingrays, moray eels, longtooth groupers (Epinephelus bruneus) wrasses like the Asian sheephead wrasse (Semicossyphus reticulatus) or the Japanese bullhead sharks (Heterodontus japonicus).
We encourage you to look at some of the videos readily available online and decide for yourself if this type of diving experience is for you.
OTHER
It’s possible to dive at an underwater hot-spring at Shikine island (Izu Islands, 3-hour boat ride from Tōkyō), which is also sometimes visited by turtles.
There is an underwater shrine, said to be the only one in the world, at the Hasama Underwater Garden (Tateyama, Chiba Pref.)
Click here for more precise, detailed and practical information on diving in the Kantō region