Macaron “This trip is a total washout.”
I’ve heard those words handful times at the Ishigaki airport, watching divers stare at the departure board as “CANCELED” flashes next to the flight to Yonaguni. The North Wind in winter is brutal—often strong enough to ground the propeller planes. But after 300+ dives on this island, I’ve learned a secret: The sky and the ocean in Yonaguni speak two different languages.
While the airport is shut down and the north side of the island is battered by white foam, the South Side is often hiding a masterpiece. Protected by the island’s towering cliffs, the water stays workable, the “Kuroshio Blue” remains crystal clear, and the hammers are waiting.
If you search the internet, you’ll find generic advice telling you to “Go in February” or “Wait for the Spring Tide (大潮).” But most of that advice comes from people who visited once.
I decided to look deeper. I’ve spent the last few months cross-referencing my personal logs from over 300 dives with local dive shop data spanning five years (2019–2024). What I found contradicts almost everything you’ve read online:
- The Spring Tide is a gamble, not a guarantee (and can actually make sightings harder).
- The “Bad Weather” forecast is often your best friend due to the “Island Shield” effect.
- The Kuroshio Current is the real boss—and its proximity to the island matters more than the moon phase.
Whether you are planning your first trip to the frontier of Japan or you’ve been “skunked” before, this guide is built on raw data and hundreds of hours in the blue. Let’s look at the reality of Yonaguni Hammerheads that the guidebooks won’t tell you.
At a Glance: The Yonaguni Reality Check
- Best Season: Late December to late March (Peak: Jan/Feb).
- The Tide Secret: Stability > Strength. Neap and Mid-tides often offer the stable East-to-West currents sharks prefer, while Spring Tides (大潮) can be unpredictable.
- The Weather Paradox: A North Wind is actually good for diving (the “Island Shield” effect), but an East Wind is the real threat to your trip.
- The Kuroshio Factor: Sightings are highest when the Kuroshio Current is “hugging” the island and the water temperature is below 26°C.
- Recommended Experience: Minimum 100 dives; proficiency in Negative Entry and drift diving is essential.
- The 4-Day Rule: Stay at least 4 days to maximize your window for perfect current stability.
Where is Yonaguni Island? (The Frontier of Japan)
Yonaguni Island, located at Japan’s westernmost tip, lies 111 kilometers east of Taiwan, making it closer to Taiwan than to mainland Japan.
The island enjoys a subtropical climate, with water temperatures ranging from 22 to 30 degrees Celsius, ideal for year-round diving in a wetsuit. With this island so small, spanning 28.88 square kilometers, access from the port to various diving spots is conveniently quick, ranging from a 2-minute to a 30-minute boat ride.
Getting to Yonaguni: Flights vs. The “Vomit Ship” Ferry
Let’s assume you’d arrive in Tokyo and enjoy some time in the city first. Then after typical sightseeing, you will be ready for the adventurous part of the trip. YONAGUNI.
The first place to go to is Haneda Airport and you will fly from there.
From Tokyo to Yonaguni
To get to Yonaguni from Tokyo, you have two options: transfer at either Okinawa (OKA) or Ishigaki (ISG).
Whether you’re flying from Naha or Ishigaki, reaching Yonaguni Island requires a connection with Japan Ryukyu Air Commuter (RAC). For travelers departing from Tokyo, the flight routes are limited to either Haneda-Naha-Yonaguni or Haneda-Ishigaki-Yonaguni.
From Okinawa to Yonaguni
Divers often opt for convenient itineraries, such as an evening flight from Haneda to Naha, an overnight stay, and a morning flight to Yonaguni, allowing for three exhilarating dives upon arrival. Keep an eye on flight options like RAC721 from Naha at 07:15 to Yonaguni at 08:35.
Recommended flights from Tokyo to Okinawa
From Tokyo, you have several airline options. JAL, ANA, Skymark and Solaseed.
All of them depart from Haneda Airport, which is conveniently located and well connected from the center of Tokyo and Yokohama. You can take a train from any Tokyu line station to Haneda or take Tokyo monorail from Hamamatsu station.
https://tokyo-haneda.com/en/access/train/index.html
There is another airline that is Peach, but them being the Low Cost Airline, leave from the outskirt of Chiba, and not from Tokyo. It is similar to taking Ryanair from Frankfurt Haan, Paris Bevais, London Stansted and the like. I am not sure if it make sense to save 20 USD to spend extra time for surface travel.
From Ishigaki to Yonaguni
For divers flying from Ishigaki, the RAC741 flight departing at 10:05 and arriving in Yonaguni at 10:40 offers a chance for two dives on the same day.
Alternative, Ferry ride from Ishigaki to Yonaguni
If you’re up for a longer stretched journey, consider the “Gero-sen” ferry operated by Fukuyama Kaiun, departing twice a week from Ishigaki. While diving on the arrival day might be challenging, this option suits those who prefer a leisurely approach to their scuba schedule. Despite its nickname, the “vomit ship,” the ferry provides a comfortable 4-hour journey with bunk beds for a surprisingly enjoyable experience.
While both the flight and the ferry are often canceled due to North Winds, don’t panic—as I’ll explain later, this weather is actually great for diving.
The Logistics Trap: Why You Must Book Accommodation First
The biggest and the most common mistake that the 1st time visitors to Yonaguni make is not securing the accomodation first.
Accommodations on Yonaguni Island are limited, especially during the peak Hammerhead Shark season from December to March. With the island attracting a considerable number of divers during weekends and holidays, securing a place to stay becomes crucial.
For those determined to encounter Hammerhead Sharks, it’s advisable to secure accommodation before diving reservations.
Are Hammerhead Sharks safe to dive with?
Known as “Shumokuzame” in Japanese, the Hammerhead Shark is a globally distributed species, often spotted around Japan’s Mikomoto Island and Yonaguni Island.
Recognized by their distinctive hammer-shaped heads, these sharks boast sharp teeth and are known for preying on fish.
Fear not, as Hammerhead Sharks are not known to pose a threat to humans. Their timid nature means they usually avoid aggressive behavior towards divers and swiftly swim away when approached. Understanding the proper approach is key to enhancing the diving experience.
Why Yonaguni Island has high Hammerheads encounter rate
Hammerhead Sharks in Japan are commonly found in areas influenced by the Kuroshio Current.
Yonaguni Island, situated along the Kuroshio Current’s path, offers a promising environment for encountering these majestic creatures. It’s believed that when Kuroshio Current collides with the island, and not overlapping, larger schools of Hammerhead Sharks love to show up in the Yonaguni sea.
Another famous location where this Kuroshio power invites hammerhead sharks is Mikomoto Island, known to be flooded with divers during summer to autumn.
Best Season for Yonaguni Hammerheads: Why Water Temperature and North Winds Matter
Yonaguni Island is synonymous with large-sized Hammerhead Sharks, with bodies ranging from 2 to 3 meters, surpassing those in Mikomoto. While the hammerhead season in Mikomoto is during the summer, the best season for encountering schooling hammerhead sharks in Yonaguni is winter.
December to March
The optimal timing varies each year, but generally, the hammerhead season is in full bloom from the end of December to late March. During this period, water temperatures of approximately 22 to 25 degrees Celsius are considered ideal, providing a higher likelihood of Hammerhead Shark sightings.
While November and April/May also offer possibilities, water temperatures play a significant role. Surpassing 26 degrees Celsius dramatically decreases the likelihood of encountering Yonaguni hammerheads.
Maximizing Hammerhead Shark encounter rate in Yonaguni
Despite your best efforts, there’s always a chance of not encountering Hammerhead Sharks during your visit to Yonaguni Island.
But after 300 dives in Yonaguni, here are definitive tips to maximize your encounter rate with big schooling sharks.
The Spring Tide (大潮) Myth: Why “Stronger” Doesn’t Mean “Better”
If you ask a group of divers when to visit Yonaguni, 90% will tell you: “Go during the Spring Tide.” The logic seems sound—more water movement should mean more sharks, right?
Wrong. After analyzing five years of dive shop logs and my own 300+ dives, the data tells a different story. In fact, some of the most consistent, “wall of sharks” encounters I’ve ever had occurred during Neap Tides or Mid-Tides.
The Problem: Oceanic Chaos
During a Spring Tide (大潮), the volume of water moving around the island is massive. This creates what I call “Oceanic Chaos.” The current doesn’t just get stronger; it becomes unstable.
In Yonaguni, you aren’t just looking for strong water; you are looking for Stable Flow.
- The Goal: A consistent East-to-West current along the South Side.
- The Reality of 大潮: The current becomes temperamental. It can flip directions between your morning and afternoon dives or start “swirling” around the points.
When the current is erratic, the hammerheads don’t “settle.” They scatter. It becomes a game of luck rather than a predictable intercept.
Why Stability Wins
During Neap or Mid-tides, the current is often more reliable. It might be slower, but it stays in that “Golden Direction” (East-to-West) for longer periods. This allows the schools to congregate in predictable patterns.
The Weather Paradox: Why the North Wind is Your Friend
In Yonaguni, a “bad” weather forecast is often a blessing in disguise. If you see a strong North Wind (北風) in the forecast, don’t panic. This brings us to what I call the “Island Shield” effect.
Because the major hammerhead dive sites—like Irizaki and Hammer Way—are located on the South Side of the island, the massive 100-meter cliffs of Yonaguni act as a natural fortress. While the North Side is battered by white-capped waves and the airport may even cancel flights due to high winds, the South Side remains relatively calm and perfectly diveable.
The “Canceled Flight” Secret I’ve sat on the boat during a screaming North Wind, looking up at the cliffs while having the best dive of my life, knowing that at that exact moment, the flights from Ishigaki were grounded. The paradox of Yonaguni is that “Flight Weather” = “Diving Weather.”
In fact, the only wind you should truly fear is a strong East Wind. Because the South Side is exposed to the East, a high-speed wind from that direction is what actually creates the “washout” conditions that stop the boats.
Key Takeaway: If your flight is delayed or the sky looks gray and windy in town, stay optimistic. As long as that wind is coming from the North, the sharks are likely still waiting for you in the calm, blue waters of the South.
Stay longer
To maximize your chances, consider multiple trips within the season or extending your stay for a couple of days.
The underwater condition can be unpredictable other than the regular encounter rate. The bad visibility can easily lower encounter rate. Staying longer definitely increases the chances of better ocean, therefore better encounter rate with hammerhead sharks.
You can always combine your Yonaguni dive travel with Ishigaki dive for Manta. Depending on your satisfaction level in a few days with hammerhead sharks diving, you can go to Ishigaki manta dives or stay longer in Yonaguni for more sharks.
Drift Dive often before coming to Yonaguni
Diving skills and experience also play a crucial role in making the most of your Hammerhead Shark encounters. Check the Underwater Etiquette section for more details about the skill requirement.
Visit Yonaguni multiple times in one season
The nature is uncontrollable. You might land Yonaguni when diving shops are struggling to find sharks. It might not be helpful to stay longer in that situation. But coming back more often to Yonaguni definitely guarantees you to bump into Shark paradise days as well.
Irizaki: Dive Spots for large schools of Hammerhead Sharks
Yonaguni Island offers several dive points where Hammerhead Shark schools are known to appear. Explore iconic locations such as Irizaki, a classic point surrounded by the south side of Yonaguni Island. This area includes points like “Minami No Ne,” “Hammerhead Rock,” and “Hammer Way,” known for attracting not only Hammerhead Sharks but also other large marine creatures.
Underwater Etiquette and Safety Tips for Hammerhead Shark Dives
Drift Diving skills
All scuba diving made in Yonaguni are drift dive. Recommended diving experience is minimum 100 dives and you’d better be diving frequently, at least every couple of months.
Approaching Sharks with Grace
The Hammerhead Shark season often sees larger groups of divers, requiring a thoughtful approach to ensure smooth interactions both underwater and on the boat. (it sometimes looks like a military training.)
Also, larger groups mean divers need to take turns to take pictures and videos of hammerhead sharks, making sure everyone gets to take a close look at sharks and keeping the school of sharks tight together, and not causing to split the school of sharks.
Do not drift away your camera!
Additionally, take extra care with valuable cameras and GoPros to prevent any unfortunate mishaps. Some people drop it while diving and some people drop it while climbing the ladder to the boat.
Be Prepared, but be spontaneous
You can only do so much to prepare well to increase your chance of diving with hammerhead sharks in Yonaguni. The best and only must do after all the dive trip planning is to enjoy.
Enjoy your stay in Yonaguni and try to be open to every encounter both underwater and overground to immerse yourself in this one and only marvelous island of Japan.
