Only two hours from downtown Tokyo lies one of Japan’s most exciting dive sites: Osezaki, in Shizuoka Prefecture. Kenji Ichimura has the story.
Contributed by
With its stunning view of Mt. Fuji, fresh, local seafood and direct access to Japan’s deepest bay, Osezaki is a destination that combines natural beauty with world-class diving. You can visit for a day trip, but staying overnight allows you to experience both the underwater world and the local culture more deeply.
Why Japan should be on every diver’s bucket list
When most divers dream of their next adventure, their minds drift toward the Red Sea, the Maldives or the Caribbean. But let me take you somewhere different—somewhere that might surprise you: Japan.
This country, often celebrated for its temples, sushi and Mt. Fuji, also happens to be one of the most extraordinary dive destinations on Earth. Diving in Japan is not just about the sea itself. It is about the contrasts, variety and discovery. Nowhere else can you find such a mix of conditions, ecosystems and marine life within just a short domestic flight.
Imagine beginning in the far north, where nutrient-rich kelp forests sway in the cold Pacific, hiding giant octopuses and schools of cod. Only a few hours later, you could be surrounded by manta rays gliding through the tropical waters of Okinawa.
Four reasons why Japan is a diver’s dream
1. Four seasons above and below
Japan is defined by its seasons, and the ocean follows the same rhythm. Spring brings schools of fish migrating north. Summer offers warm, clear waters for coral reef diving. Autumn turns kelp forests into a blaze of activity, while winter draws in deepwater species rarely seen elsewhere. Unlike most destinations, where you choose one climate, Japan offers them all—cold, temperate, subtropical and tropical—within the same trip.
2. A coastline that nurtures life
With 6,852 islands and nearly 34,000km of jagged coastline, almost Earth’s diameter, Japan creates countless bays and channels where life thrives. Its fishing culture has remained small-scale and coastal, helping preserve rich ecosystems close to shore. For divers, this means vibrant sites just minutes offshore.
3. The ocean currents: Nature’s grand exchange
Few places on Earth lie at the crossroads of such powerful forces. From the south, the warm Kuroshio Current sweeps up tropical life. From the north, the cold Oyashio Current pours down nutrients. Where they meet, magic happens. Near Tokyo, divers may encounter both tropical reef fish and cold-water species on a single dive, a rarity anywhere in the world.
4. Deep trenches, rare encounters
Just off Japan’s coast, the seabed plunges into trenches over 2,000m deep. Upwellings stir life from below, sometimes carrying rare, deep-sea creatures into recreational depths. With the right timing, a diver may witness species normally reserved for submersibles and documentaries. These unexpected encounters make Japan unforgettable.
A nation of ocean treasures
Together, these factors make Japan one of the richest marine environments on Earth. In fact, 14.6 percent of the world’s 230,000 known marine species live here, nearly one in seven.
Hokkaido offers encounters with the giant Pacific octopus. Off Ito, hundreds of Japanese hound sharks gather in one place. At Mikomoto, hammerheads sweep by in raw ocean power. In Okinawa, manta rays glide through turquoise seas above coral gardens.
Every dive site tells a different story, shaped by Japan’s geography, currents and seasons. Yet, all of them are connected by Japan’s world-class domestic travel network, making it possible to experience an extraordinary variety in a single journey.
The spirit of Japanese diving
What makes diving in Japan so captivating is not only the biology but also the culture that surrounds it. After a day underwater, you might soak in a steaming hot spring while gazing at snow-covered peaks, or enjoy the freshest sushi, caught from the very waters you explored. Diving here becomes more than time underwater, as it is a journey into Japanese life itself, blending ocean, tradition and hospitality.
Sacred Cape where ocean, culture and myth intertwine
If there is one place that symbolizes this fusion, it is Osezaki. At the northwestern tip of the Izu Peninsula, a narrow cape juts boldly into Suruga Bay. Because of its shape, it has long been nicknamed Biwa Island, after the traditional Japanese lute.
According to legend, the cape was created in 684, when a massive earthquake lifted the seabed, forming a new island. Over centuries, sandbars connected it to the mainland, leaving today’s iconic landform, a place where geology, myth and spirituality meet.
Osezaki Shrine: Where the Sea God dwells
At the cape’s tip stands Osezaki Shrine (Hikitechikara-no-Mikoto Shrine), whose origins date back more than a thousand years. It appears in the “Engishiki Jinmyocho” of the 10th century (an over 1,000-year-old shrine registry from the Heian era), marking it as one of Japan’s ancient sanctuaries.
The enshrined deity is Hikite-chikara-no-Mikoto, worshiped as a god of the sea. Fishermen and sailors once prayed here before setting out, and today, divers continue the ritual, bowing for safety before entering the ocean.
The shrine’s small hall faces Suruga Bay and is adorned with intricate carvings of dragons. Standing before it, one feels less in front of architecture than at a threshold to the divine.
Sacred trees and Dragon God
Surrounding the shrine is a forest of junipers (Byakushin), designated a National Natural Monument. Estimated to be 800 to 1,500 years old, their twisted trunks resemble the coils of dragons. For centuries, these trees have been believed to house the spirit of the Dragon God, guardian of the cape and its waters.
Hidden within the grounds lies the Kamiike Pond. Despite sitting at the tip of a cape surrounded by seawater, the pond holds only fresh water. Counted among the “Seven Wonders of Izu”, it too is said to shelter the Dragon God, strengthening Osezaki’s aura as a place where nature and the supernatural converge.
The rise of a diving sanctuary
Osezaki’s reputation as a diving site is more recent. After World War II, swimmers flocked to its shores. With the opening of the Tokaido Shinkansen (high-speed rail line) in 1964 and highways in the 1970s, access improved dramatically. By the early 1980s, divers were drawn to its clarity. In 1983, the first dive service opened, and in 1985, after careful negotiations with local fishermen, Osezaki was officially recognized as a dive site.
Since then, Osezaki has become one of Japan’s most celebrated diving destinations, embodying not only marine diversity but also the bond between sea, culture and community. To this day, many divers begin their dives not just by checking equipment, but by seeking the blessing of Hikitechikara-no-Mikoto before slipping beneath the waves.
Location and accessibility
Osezaki is in Numazu, on the edge of Suruga Bay, the deepest bay in Japan at over 2,000m. This unique geography creates powerful, nutrient-rich currents that attract a stunning variety of sea life.
Getting here is easy. By car or train from Tokyo, you can arrive in just a couple of hours. That makes Osezaki one of the most accessible, world-class dive spots in Japan.
Above the waterline
Osezaki’s scenery above water is just as unforgettable. On a clear day, divers are greeted by the iconic view of Mt. Fuji rising over the bay. The area is also famous for its fresh seafood and Shizuoka’s green tea, making it as enjoyable topside as it is underwater.
For divers who want to stay close to the action, Nature Inn Osekan offers accommodation right at the shoreline. The inn doubles as a dive shop and underwater photography center. It even features a Seacam show space, where divers can explore high-end professional housings used by some of the best photographers in the world. After a day of diving, guests are treated to fine meals created by a chef who once cooked for the Emperor of Japan, blending Japanese and French flavors into a dining experience as memorable as the dives themselves.
Diving at Osezaki
The diving here is as diverse as the scenery above. Beginners can explore the calm inner bay, perfect for first dives and training. Experienced divers head to the outer point, where rocky slopes, sandy bottoms and steep drop-offs open into deepwater habitats.
Because Osezaki connects directly to Suruga Bay, divers encounter both warm-water tropical species and cold-water, deep-sea creatures. Every dive is different, and every photograph tells a new story.
The anthias of Osezaki
One of the most magical sights at Osezaki is the world of anthias. These small, colorful fish gather in dazzling schools, turning the reef into a living cloud of pink, red, orange and yellow. For photographers, anthias are both a challenge and a reward, as some are common and easy to find, while others are rare treasures hidden in the deep.
Globally, scientists recognize well over 200 anthias species, across about 25 to 30 genera. The exact number shifts as new species are discovered, but this wide family is found throughout tropical and subtropical seas. Against this backdrop, the fact that Osezaki alone hosts 18 documented species is extraordinary. For a single shoreline site to hold such diversity makes it one of the richest anthias habitats in the world.
This is not a promise, though. No dive site ever guarantees what you will see. Marine life depends on currents, seasons and pure chance. But Osezaki is special because of the mix of shallow-water residents and deepwater rarities, which means the more you dive here, the more the site reveals itself. With patience and return visits, divers can experience an unfolding story of anthias unlike anywhere else.
Shallow-water anthias (1-15 m)
Goldfish anthias (Pseudanthias squamipinnis) ☆☆☆☆☆ – The most abundant anthias at Osezaki. Their bright orange bodies gather in huge schools over shallow reefs, shimmering in the sunlight like curtains of fire.
Redbelted anthias (Pseudanthias rubrizonatus) ★☆☆☆☆ – Once a rare deepwater sight, now a regular resident from 15 to 50 meters. The bold red stripe across its body makes it one of the most striking fish at Osezaki.
Mid-depth anthias (15-40 m)
Bicolor anthias (Pseudanthias bimaculatus) ★★★☆☆ – A mid-depth treasure, glowing yellow at the front and purple or pink at the tail. Males are bold and dramatic; females are softer and pastel.
Kerama anthias (Pseudanthias rubrolineatus) ★★★☆☆ – Visitors from southern waters, now showing up more often in Osezaki. Their unique color patterns set them apart from the crowd.
Cooper’s fairy basslet (Pseudanthias cooperi) ★★★☆☆ – Found schooling above rocky reefs, glowing pink and orange with a fiery look when lit by sunlight or strobes.
Princess anthias (Pseudanthias smithvanizi) ★★★☆☆ – Quiet and graceful, hovering in small groups at 20 to 30 meters. Their subtle colors come alive under the camera’s flash.
Deepwater anthias (30-60+ m)
Cherry anthias (Pseudanthias fasciatus) ★★☆☆☆ – Shining in pink and cherry red, these elegant fish appear between 30 and 50 meters, glowing against the deep blue.
Longfin anthias (Pseudanthias elongatus) ★★☆☆☆ – With long trailing fins, they hover gracefully at 30 to 50 meters, standing out from the faster anthias around them.
Sailfin anthias (Pseudanthias ventralis group) ★★★★☆ – Rare and unforgettable. Males flash their fins in rhythmic displays that look like an underwater dance.
Threadfin anthias (Pseudanthias ventralis) ★★★★☆ – At 40 to 50 meters, this pastel pink-and-gold anthias glows under strobes, one of the most photogenic deepwater fish in Suruga Bay.
Stripe anthias (Pseudanthias grammoptilus) ★★★☆☆ – Usually seen in small numbers, calmly hovering in the dim blue, giving a sense of mystery to the deep reef.
Benihana anthias (Pseudanthias sp.) ★★★☆☆ – A not-yet-described species, found between 30 and 40 meters. A reminder that the sea still holds secrets.
Spotted anthias (Pseudanthias flavoguttatus) ★★★★☆ – Usually seen as juveniles, at 40 to 50 meters. Adults have golden spots, but the young glow with a softer, almost see-through beauty.
Japanese paranthias (Paranthias colonus group) ★★★★☆ – Only juveniles appear here. Smaller, brighter and more delicate than their powerful adult form elsewhere in the Pacific.
Checked swallowtail (Odontanthias rhodopeplus) ★★★★★ – I have only seen this once in over 2,000 dives. It appeared suddenly, glowing like a jewel against the dark reef.
White-bar anthias (Pseudanthias leucozonus) ★★★★★ – Another one-time encounter. Though rare, it remains one of my favorites for its unique markings and the memory of that single sighting.
Slender anthias (Luzonichthys waitei) ★★★★★ – A deepwater schooler, usually below 40 meters. Delicate, slim and shimmering, it is a prized subject for photographers willing to go deep.
Red-saddled basslet (Pseudanthias flavoguttatus group) ★★★★★ – Found around 60 meters, marked by a bold red saddle across its back. Exceptionally rare, almost never seen and unforgettable when it appears.
Diving for everyone
Osezaki has something for every level of diver. Beginners enjoy easy shore entries in calm conditions. Experienced divers explore the outer slopes, with their mix of reefs and drop-offs. Technical divers descend into deep water, chasing rare species and unforgettable encounters. This wide range of possibilities makes Osezaki truly special.
Where the ocean, the divine and people meet
Osezaki is not only about diving. It is also about the community, the people and the culture that welcome visitors from around the world. Local dive shops and inns create a warm atmosphere, connecting divers to the sea and to the traditions of the area.
Walking beneath thousand-year-old junipers and gazing at the shrine’s ornate hall or reflections on the mysterious Kamiike (God Pond) enriches the experience beyond the water. With Mt. Fuji rising across Suruga Bay and the Japan Trench just offshore, Osezaki embodies both the natural power and spiritual heart of the country. For divers around the world, Osezaki is not simply a destination. It is a pilgrimage.
Closing reflections
After more than 2,100 dives, Osezaki still inspires me. Each dive brings something new, from endless schools of anthias to rare, deepwater encounters. For me, diving here is more than just exploration. It is sharing Japan’s underwater treasures with the world. Osezaki is not just a dive site. It is a gateway into the deep heart of Japan. ■
