The Tsugaru Strait Channel Crossing: Final Summary and Next Steps

The Tsugaru Strait Channel Crossing: Final Summary and Next Steps


As we explore the information surrounding the Tsugaru Strait and the Oceans Sevens, we find it essential to clarify our role.

Administrative Role Defined

Much like the captain of a ship ensuring smooth sailing without dictating the destination or the currents of the sea, an administrative role is about overseeing, organizing, and facilitating. It’s about ensuring that the voyage – or in this case, the research – is conducted methodically. It does not involve setting the course or governing the tides.

We’d like to emphasize that WOWSA stands not as a governing body over the Oceans Seven or its channels, but rather as a dedicated crew, volunteering our time and resources. Our compass is set towards understanding and documenting, not ruling or regulating.

Our voyage into this research is not without challenges. The time we’ve dedicated and the resources we’ve allocated, especially for translations, are considerable. But like any worthy expedition, we believe in the importance of charting these waters for the collective knowledge of our community.


By directly engaging with local organizations and experts with extensive experience in the Tsugaru Channel, we aimed to dispel prevailing misconceptions by presenting a well-researched and factual overview. Our goal is to provide a clear and grounded assessment, enabling the open water swimming community to gain an accurate understanding of the situation to facilitate informed and constructive action.

Nature of the Tsugaru Strait:

The strait is known for its strong winds and currents, often surpassing human capabilities. Recent changes in sea conditions have made it increasingly challenging to predict the currents, their strength and timing.

The Kuroshio Current, which affects the Tsugaru Strait, is influenced by various factors and tidal forces. The Kuroshio Current consists of the current flowing from the East China Sea through the Tsushima Strait into the Sea of Japan, and the main current that continues to flow northward along Japan in the Pacific Ocean. The current that passes through the Tsushima Strait flows north along the coast of Japan in the Sea of Japan, and then goes through the Tsugaru Strait into the Pacific Ocean.

Environmental Challenges:

  • The Tsugaru Strait’s unpredictable nature, influenced by factors like the 2011 Tohoku earthquake and the Kuroshio Current, poses significant challenges for swimmers.
  • The rapid changes in sea conditions, as reported by local fishermen, make it increasingly difficult to predict currents.
  • While climate change has affected fish types in the Tsugaru Strait, it hasn’t rendered the channel swim impossible.

Timing & Conditions:

  • The best time to swim is around the summer solstice in June/July.
  • Post the earthquake on March 2011 in the Tohoku region of Japan, fishermen reported faster currents in the Tsugaru Strait.
  • Mr. Ishii noted that the currents in 2023 are particularly fast. Historical swims had better conditions.
  • June has a northeastern wind causing choppy waters, suitable for cold water swimmers.
  • July is the rainy season, making it less ideal for swims. It is also a time when fishermen prefer not to have swimmers around.

Coast Guard Rules, Regulations, Fishermen, and Routes in the Tsugaru Strait:

The Tsugaru Strait is an international strait frequented by warships and cargo vessels from countries like China and Russia. Recent geopolitical events, such as North Korean missile launches and Russian warship movements due to the Ukraine conflict, have added complexities to navigating the strait.

The Japanese Coast Guard’s cautious approach, influenced by both historical attitudes and current geopolitical events, means that swimmers face stringent regulations. The prohibition on nighttime swimming remains a significant challenge. Any major accident or mishap in the strait could lead to stricter regulations or even a potential ban on future swims.

Coast Guard & Regulations:

  • The Japanese Coast Guard has historically been skeptical about Tsugaru Strait swims, emphasizing safety.
  • Recent geopolitical events, such as North Korean missile launches and Russian warship movements due to the Ukraine conflict, have added complexities to navigating the strait.
  • Nighttime swimming has always been prohibited by the Coast Guard. This is not a new regulation.
  • Swims must be completed from sunrise to sunset.
  • Having the Coast Guard’s stamp of approval can make interactions with territorial fishermen smoother.
  • While the Japanese Coast Guard can issue warnings, they cannot outright ban swims.
  • Swimmers must submit paperwork detailing the time and rules they’ll follow to get the Coast Guard’s approval.
  • Previously, a “report”( 届 : todoke) was required to inform the Coast Guard about the swim, but now a simple notification (お知らせ: oshirase) suffices.

Local Concerns:

There’s a delicate balance between the interests of swimmers and local fishermen. The territorial nature of fishermen, especially near Fukushima, and the overlap of peak swimming and fishing times in June and July, can lead to potential conflicts. June and July are peak times for both swimming and fishing. Good days for swimming often coincide with optimal fishing days.

  • Fishermen are territorial about the 2-3 nautical miles from Fukushima coast, which is their primary fishing area. This territorial nature might have influenced Ocean-Navi’s decision to avoid landings to the East in Shirakami near Fukushima.
  • Post the 2011 earthquake, fishermen reported faster currents in the Tsugaru Strait. This is in reference to David Yudovin, Steven Munatones, Miyuki Fujita which were before the earthquake.
  • Sea conditions have been changing rapidly in recent years. According to local fishermen, it has become very difficult to predict the time of day and area where the currents will occur, as well as their strength.

Routes & Landing Locations:

  • Fukushima (East Shirakami): Not welcoming to swimmers but will accept them if they arrive. Ocean-Navi might avoid landings to the East in Shirakami near Fukushima due to the territorial nature of fishermen.
  • Matsumae (West Shirakami): A possible landing spot, but it’s rare unless during high tide.

Tsugaru Strait Observers and Pilots:


Since 2008, Ocean-Navi facilitated Tsugaru Strait swims, welcoming 142 swimmers/groups and seeing 70 successful crossings (44 solos, 26 relays). Recent years have seen a series of challenges associated with their operations and faced significant criticisms regarding their operations, communication, and transparency this year. They recently decided to stop services for international swimmers.

Pricing and Costs:

  • Charges: Ocean-Navi is known to charge 6,000 euros for facilitating a Tsugaru Strait swim, making it the most expensive among the Oceans Seven challenges.
  • Payment Demands: Swimmers have reported that Ocean-Navi demands full payment many months in advance of the swim.
  • Cost Increases: Over the years, the costs associated with Ocean-Navi swims have risen dramatically. In addition to the base fee, they have introduced an overtime charge. The charge is 900,000 Yen for the first 10 hours, followed by an additional 20,000 Yen per hour for the next four hours.

Time and Slot Restrictions:

  • 14-hour Rule: Introduced in 2022, this rule mandates that swimmers have a maximum of 14 hours to complete their swim. The first swimmer of the season was stopped at the 14-hour mark.
  • Slot System: Ocean-Navi has implemented a 5-day window system for swims. This window is shared between two swimmers. The first three days are reserved for the first swimmer, and the remaining two days for the second. If the first swimmer starts early, the second swimmer gets the remainder of the 5-day slot. If the first swimmer doesn’t swim within the first three days, they forfeit their opportunity.
  • Month Restriction: Ocean-Navi reportedly offered these 5-day windows back-to-back only for the month of July.

Communication and Transparency Issues:

  • Pledge Document: Just before the swim, swimmers are presented with a document titled “Pledge.” This document, among other things, requires swimmers to agree not to complain publicly if they are pulled out of the water for any reason.
  • Night Swimming: Pre-trip communications mentioned the possibility of night swimming, which is generally considered advantageous due to calmer waters and currents. However, upon arrival, swimmers found out that night swimming was not allowed.
  • Landing Restrictions: Swimmers were not informed about the new rule prohibiting them from ending their swims east of Cape Shirakami until their arrival in Aomori.
  • 14-hour Rule Communication: Ocean-Navi admitted that the 14-hour rule was communicated in the Japanese documents but was missed in the English versions for international swimmers. This oversight led to confusion and frustration among many participants.

Refund Policy:

  • Ocean-Navi offered a 25% refund for swimmers who do not start their swim. However, if the swim had started, no refund is provided.

Swimmer Experiences:

  • Swimmers expressed concerns about Ocean-Navi’s competence in choosing the right window for the swim, especially given the limited availability of slots.
  • Some swimmers felt that Ocean-Navi’s communication was not their strong point, although interactions with individual staff were generally positive.
  • The introduction of new rules without prior communication has been a significant point of contention for many swimmers.

Ocean-Navi’s Response:

  • Ocean-Navi acknowledged some of the issues, especially the oversight in communicating the 14-hour rule in English documents. They have apologized for the confusion and inconvenience caused.
  • Given the challenges and constraints, Ocean-Navi decided it will not accept international swimmers in the future. Those who have already applied or are on the waiting list will be contacted individually.

2023 Tsugaru Swim Attempts

Ocean Navi:

  1. Chen Suwei (China): Started at 3:37am, swam for 14 hours covering 41km. Stopped due to reaching the time limit.
  2. Paul Feltoe (NZ): Started at 3:32am, swam 34km in nearly 12 hours. Stopped due to a strong side current from the west.
  3. Michael Payne (Australia): Initially postponed due to illness. Started at 3:52am, swam 35km in 9 hours and 39 minutes. Stopped 5 miles from Cape Shirakami due to a strong current with a speed of 6.1 knots per hour.
  4. Paul Georgescu (Romania): Started at 3:52am, swam 31.85 km in 10 hours and 38 minutes. Stopped due to increasing current speeds of 4 knots per hour.
  5. Takaomi Modegi (Japan): Swim was cancelled due to weather
  6. Edie Hu (China): Swim was cancelled due to weather
  7. Dean Summers (Australia): Started at 3:56am, swam 19.5km in 8 hours 33 minutes. Stopped because told he would be pulled at 10 hrs. The swim was stopped due to a strong current towards Cape Tappi, Aomori.
  8. Popova Liudmila (Russia): Started at 3:59am, swam 16.7km in 8 hours 38 minutes. Stopped due to a strong current from the north-west.
  9. John “Batches” Batchelder (USA): Swim was cancelled due to weather/time slot expiration
  10. Sarah Thomas (USA): Swim was cancelled due to weather
  11. Rob Lea: Swam for 8 hours and 19 minutes, covering about 21km. Chose to retire after being informed he wouldn’t make the 14-hour time limit.
  12. Red Sea Crossing Team SA/50 (Japan): 10 hours after the start, retired at the 21km point.
  13. Bárbara Hernández (Chile): Swim was cancelled due weather

Cancelled Swims:

  1. Takaomi Modegi (Japan)
  2. Edie Hu (China)
  3. John “Batches” Batchelder (USA)
  4. Sarah Thomas (USA)
  5. Bárbara Hernández (Chile)

Total cancelled swims: 5

Swimmers who started and their respective distances and times:

  1. Chen Suwei: 41km in 14 hours
  2. Paul Feltoe: 34km in 12 hours
  3. Michael Payne: 35km in 9 hours and 39 minutes
  4. Paul Georgescu: 31.85km in 10 hours and 38 minutes
  5. Dean Summers: 19.5km in 8 hours 33 minutes
  6. Popova Liudmila: 16.7km in 8 hours 38 minutes
  7. Rob Lea: 21km in 8 hours and 19 minutes
  8. Red Sea Crossing Team SA/50: 21km in 10 hours


  • Number of cancelled swims: 5
  • Average distance swum: 27 km
  • Average time swum: 10 hours

Historical Ocean-Navi Swim Data

YEARSOLO/RELAYDNS/DNFTotal Swims% Successful Swims
20172 solo/relay101216.67%
20184 solo/relay91330.77%
201913 solo/relay122552.00%
20224 solo/relay71136.36%
20230 solo/relay13130.00%
See resources below

2023 Tsugaru Swim Attempts – Tsugaru Strait Swimming Association (Mr. Ishii):

Completed 19.5 km Tsugaru Strait

  1. Andy Donaldson – Swam 37.6+ km in 13hrs 4mins 30secs (Landed East of Shirikami)

Note: Mr. Ishii stated: “I think our difference from Ocean Navi is this “strength of resolve.” Of course, Andy’s excellent swimming ability was the biggest factor in his success, but perhaps his mental strength of “I will swim to Hokkaido no matter what” led him to success.

Organizing Bodies

While Ocean-Navi has been the primary facilitator, the information suggests that swimmers don’t necessarily need to be affiliated with any organization to attempt the swim. Swims in Tsugaru Strait in the past have been organized independently. Other Oceans Seven channels for example Kaiwi Channel swims are ratified by the pilots and/or observer.

Rules and Ratification Historical Considerations:

  • Ocean-Navi’s approach to swim management was perceived as not recognizing the fundamental rules of channel swimming, use of streamers, night swimming in the past.
  • Swimmers don’t need to be affiliated with any organization to attempt the swim, as long as they adhere to the Oceans Seven rules and have an observer. (Both Ocean-Navi and Mr. Ishii)
  • Observers don’t require formal training but must be knowledgeable about certain aspects of the swim.
  • Some pilots have been criticized for their inexperience and mishandling of past incidents.
  • Historically there are other Japanese swimmers who have completed the Tsugaru Strait crossing not on the Oceans Seven Tsugaru Channel list of successful swims.

Timing and Landing Considerations:

Even though it was always against Japanese Coast Guard regulations, 17 of 42 of the successful Ocean-Navi swims between 2011-2022 (40.48%) were night swims. Six swims were over 14 hrs. So more than half of the swims would not be possible today with a 14 hour cutoff. We have not found time to examine where all swims landed but from an initial analysis of route maps of 22 of the 42 swims handled by Ocean-Navi, we find that 12 (54.55%) of the 22 swims finished East of Shirakami.

Blue highlight are night swims. Gathering start times was difficult. Ocean-Navi has removed there records from the site recently. See table of Ocean-Navi DNF, DNS in resources. Orange highlight are over 14 hours.

Full Goggle Sheet

Training & Future Prospects:

  • Mr. Ishii is 70 years old and his pilot Mr. Mizushima, is 77 and can handle 2 or so swimmers a year and he will retire in a few years.
  • WOWSA asked if Mr. Ishii would considering mentoring new observers. There might be an opportunity to establish an observer training school post March 2024, after Mr. Ishii concludes his swimming school.
  • If Mr. Ishii were to train someone, he’d need to be on the water with them in Tsugaru, raising questions about boat arrangements and costs.
  • WOWSA will be organizing an initiative to prepare a text book about Tsugaru Channel and observer training manual written by Mr. Ishii so that there is textbook as a first initiative to aid the future of this route. A training manual for future observers is a step to preserve the knowledge necessary to cross the Tsugaru Straits for future swimmers and generations.

Recommendations for Swimmers:

  • Organizing independent swims is feasible but comes with challenges, including communication barriers with Japanese boat pilots and obtaining permissions from the Coast Guard.
  • Carelessness during swims can lead to accidents. Serious or tragic accidents could result in a potential ban on future swims in the Tsugaru Strait.
  • The boat pilot’s knowledge and experience plays a crucial role in navigating the strait, emphasizing the importance of understanding the currents and winds of the Tsugaru Strait.
  • Familiarize yourself with the international rules of channel swimming and ensure anyone you work with adheres to these standards.
  • Choose the Right Route: The starting point and route can play a significant role in the success of the swim.
  • Prepare for Communication Challenges: If organizing an independent swim, be prepared for potential communication barriers with Japanese boat pilots as they speak in a dialect.
  • Adhere to Coast Guard Regulations: Ensure you are aware of and adhere to all Coast Guard regulations, especially those related to swim timings.


While the Tsugaru Strait swim remains a prestigious Oceans Seven challenge for marathon swimmers, its future is uncertain. The combination of organizational challenges, geopolitical tensions, environmental unpredictability, and local concerns makes it a complex effort but not impossible. The waiting lists and bottlenecks for channel swims are long at multiple channels in the Oceans Seven circuit. The most pressing issue in Tsugaru is lack of trained qualified observers and experienced pilots. However, if there is interest, constructive efforts and active initiatives by the international swimming community, it might pave the way for a new chapter in the history of Tsugaru Strait crossings and is not an unfeasible prospect.

Our next report will cover all the channels in the Oceans Seven.

Please report corrections or edits to

Call to Action:

A first step toward preserving the legacy of the Tsugaru Strait Crossing and the Oceans Seven.

WOWSA is embarking on a mission to create a comprehensive textbook about the Tsugaru Channel, complemented by an observer training manual written by Mr. Haruyuki Ishii of the Tsugaru Strait Swimming Association. This initiative aims to preserve the legacy and intricate knowledge of crossing the Tsugaru Straits for the benefit of future swimmers.

Pre-order: By pre-ordering this book and manual, you’ll gain early access to the book and support its creation and translation. By backing this initiative, you’re not merely buying a book; you’re ensuring the legacy and knowledge of Tsugaru Channel swimming endures for future generations.


Historical Research


Ocean-Navi Records (were on this page now removed 8/2023) Google Sheet