Tsubame was a Japanese naval vessel built after World War I. During World War II, she was attacked by U.S. forces and sank off Miyakojima on March 1, 1945. The ship still rests on the seafloor, quietly marking the passage of time together with those who died. However, her exact location has not yet been confirmed.
This project is being pursued in response to a direct request from the family. We consider it an effort of exceptional significance—both as an opportunity to honor the wishes of the bereaved family, and as an undertaking that contributes to war remembrance as well as the investigation and preservation of underwater cultural heritage.
Whether the ship can be found remains uncertain. Still, if our technical capability can help—even in part—and support remembrance and further research, we would be grateful.
Tsubame was the lead ship of the Tsubame-class minelayers, built in Japan after World War I. The sister ship of the same class was Kamome. According to Nihon Kaigun Go’eikan-tei Shi, the Tsubame-class is positioned as a prototype of a modern-style minelayer.
At that time, minelayers were vessels intended to lay naval mines, anti-submarine nets, and navigation markers. During wartime, their roles expanded to include missions such as coastal defense and convoy escort.
Both Tsubame and Kamome were lost in the Southwest Islands area (from the southern tip of Kyushu to northeast Taiwan). This project focuses on Tsubame, which sank off Miyakojima on March 1, 1945.
Principal particulars
subame was a relatively small warship, with a wartime planned complement of approximately 80 personnel.
According to Sakishima Islands Operation (Miyako Volume), Tsubame departed Sasebo on February 13, 1945, escorting two transport ships. Despite being attacked several times along the way, she arrived at Miyakojima on the evening of February 29. The next morning, around 7:00 a.m. on March 1, she came under air attack by U.S. fighter aircraft and sank around 5:00 p.m. It is stated that more than 70 personnel, including Captain Takeo Yoshida, were killed in this battle.
Other records indicate that around 40 surviving crew were incorporated into existing forces on Miyakojima. Because these figures do not align cleanly with the planned complement, it is believed that accurate records of casualties may not remain.
Even the type of attacking U.S. aircraft is unclear: some sources describe it as F6F Hellcat, others as F4U Corsair, and misidentification was reportedly common at the time.
Although I have dived many war wrecks, at first I did not have sufficient knowledge about Tsubame. The turning point was meeting Takamatsu Gushiken, who continues remains-recovery activities related to the Battle of Okinawa. Through connections formed him, I was approached around February 2025 with information that a bereaved family member was seeking advice regarding an underwater exploration of Tsubame.
After conducting more detailed interviews in autumn 2025, it became clear that the requester was Susumu Yoshida, the eldest son of Tsubame’s captain, Takeo Yoshida. I also learned that searches had been attempted in the past with cooperation from a local dive shop, but the wreck had not been found. Considering Mr. Yoshida’s advanced age, I felt the exploration should be pursued without delay.
From the materials provided, we confirmed the following situation:
The bereaved family’s wishes regarding recovery were also featured on NHK “Ohayo Nippon” (April 10, 2025), where Mr. Yoshida’s feelings were shared.
The handling of underwater human remains has also drawn increasing social attention in recent years. As described on the project page, the government stated a policy in 2020 to proactively collect information when there is a risk that the dignity of remains may be harmed; however, because Tsubame itself has not been found and remains are not exposed to public view, it is not currently included in official national investigation targets.
Considering the fact that previous dives have failed to find the vessel, the following possibilities are possible regarding the current state of the Tsubame.
Given that the charted depth is relatively shallow (25 m) and the wreck remains undiscovered, it is also possible that the hull is damaged or buried in sand, which would make the search extremely difficult.
On the other hand, even if a hull has broken apart, items such as ceramics often endure corrosion and remain. If the chart position is correct and the site is not buried, there may still be a chance of discovery. Additionally, if the true wreck site lies deeper than the charted position, the likelihood that the hull remains more intact may increase.
Based on these considerations, preparations began to conduct the survey as early as possible.
Before diving a wreck, I make it a habit to study its history and, when possible, plans and drawings. This is both because “diving a wreck can be seen as diving into its history,” and because understanding the structure improves safety and efficiency in the field.
For Tsubame, however, available materials were extremely limited and information on internal layout and structure was fragmentary. In that situation, we identified an individual who had created and published illustrations from drawings for model-building purposes. After making contact, we were kindly granted permission to use those illustrations. The page notes that these materials are valuable not only for understanding the hull structure, but also for improving search effectiveness and exploration safety.
Mr. Susumu Yoshida had previously asked DIVE Miyakojima (Owner: Hirokazu Sunagawa)—a long-established local dive shop run for more than 30 years—to attempt underwater searches. This shop is also where Mr. Yoshida and his sun and daughter had enjoyed recreational diving.
For this project, we contacted Mr. Sunagawa in advance and conducted an on-site meeting (with media presence) to confirm previous search efforts, understand the current situation, and align on future direction.
DIVE Miyakojima
Mr. Hirokazu Sunagawa
Nautical chart of the location where Tsubame sank
Among the materials provided by Mr. Yoshida was a record from a January 30, 1982 memorial service, including a “Miyako Islands map” marking a point labeled “Tsubame.” A wreck symbol was also shown in the same area on a nautical chart Mr. Yoshida had photographed.
Because the production date of that chart was unclear, the latest charts were checked. Two nearby wreck symbols were identified:
From interviews with Mr. Sunakawa, testimony was obtained that at the 45–50 m location, sonar had detected a response believed to be an artificial structure. This increased the possibility that the hull may remain to some degree in recognizable form at that deeper point.
Both candidate points lie directly beneath a shipping route and are not places where recreational divers can normally dive—consistent with why the wreck may not have been found to date.
Information was also shared that a memorial monument may be visible near the southern end of Karimata Beach. Although it could not be confirmed that day due to bad weather, the monument is also described in the 1982 memorial-service materials, and the page notes it may be a memorial for Tsubame. If confirmed, it would be a strong piece of evidence supporting the sinking in this area.
During the visit, we also met with local media in Miyakojima and were able to gather valuable documents and information related to Tsubame, with gratitude expressed to all who cooperated.
Mr. Susumu Yoshida visits Miyakojima every year on March 1—the date of Tsubame’s sinking—to continue paying his respects. After discussions with Mr. Yoshida and Mr. Sunakawa, the project set its policy to conduct the dive exploration around this memorial period.
As of the plan described on the page, the exploration is scheduled for approximately March 1–March 4, 2026, using the vessel of DIVE Miyakojima, which has supported prior search efforts.
Because the exploration areas lie directly beneath shipping routes, the plan prioritizes safety: the team intends to use large DPVs (underwater scooters) to move out of the route area and conduct dives with safety as the highest priority.
Multiple pieces of information obtained during the November 2025 visit are important clues toward confirming the wreck location. In particular, investigating the 45–50 m point where a sonar response has been reported is expected to be a central focus of the dive exploration.
Going forward, we aim to proceed in close cooperation with the bereaved family, local stakeholders, and administrative bodies, and to confirm and preserve records of the wreck in a manner that is both safe and ethical.
Affiliations may not be up to date.
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