Tsugaru Strait Channel Research (Part 4) – Getting to the Root of the Ocean-Navi Routes, Rules and Start Times

Tsugaru Strait Channel Research (Part 4) – Getting to the Root of the Ocean-Navi Routes, Rules and Start Times


As we examined in the previous post, Tsugaru Strait Channel Research (Part 3) – Exploring Rules, Streamers, and the Absence of a Local Governing Body there is still some ambiguity around if there is a local governing body and what rules are being followed. The rules issue is still being investigated. Ocean-Navi said there is no TCSA. In Andy Donaldson recent successful swim, Ishii was the observer but we have not confirmed if TSSA still exists.

Start Times

In our previous post, In-Depth Discussion with Ocean-Navi: Tsugaru Strait Channel Research (Part 2), we covered these issues

  • There is no law specifically stating that swimming before 3 am is prohibited.
  • There is a 14-hour time limit for the swim that was established in 2022.
  • Captain will charge extra after 10 hours
  • Special permission to swim before 3 am is not granted. There is no exception or possibility to bypass the rule and swim at night.
  • Ocean-Navi made these rules in consultation with the captain and enforces them.
  • Time is fixed in 2023 to 4:00 AM.

Ocean-Navi has sent us route maps for 22 (up until 2018 so far*) of the 42 swims they handled. From those 22, six (27.27%) of the successful swims so far were night swims (starting before 3:00 AM).

*We asked for all swim records, so we do not understand why they omitted post 2018 (pending)

Lines are not official shortest point A to point B distances but show various routes swimmers have taken historically in Tsugaru Strait for both TSSA and TCSA swims.

Start and Finish Locations

For TSSA historically there are 3-4 routes (see resources). For Ocean-Navi, from Honshu to Hokkaido, the route typically starts at Kodomari and ends at Cape Shirakami. The issue this year was a change as to what side of Cape Shirakami the swimmer lands on. When we asked if this is a rule and if the Japanese Coast Guard has enforced it Ocean-Navi answered

From Ocean-Navi:

We check the sea situation at the start and change point sometimes, but always around Gongenzaki area in Kodomari Town. Arriving points are depending on swim situation. Sometime at the west of Cape Shirakami, sometimes at the east of Cape Shirakami. There’s no rule for that.  

Since last year, after the fatal accident of a pleasure boat in Hokkaido, which became a nation-wide news for days and weeks, Japan Coast Guard got more inflexible and now we are only allowed to swim in the certain range we get permission beforehand.  


While the details are not entirely confirmed. It appears they need to get permission for the route beforehand. Since Andy Donaldson recently landed East of Shirakami we can assume it is possible to get permission to swim to the East of Shirakami.

If we examined the route maps below which are only 22 of the 42 swims handled by Ocean-Navi, we can see that 12 (54.55%) of the 22 swims finished East of Shirakami.

Haruyuki Ishii’s Perspective on Routes

From Haruyuki Ishii’s blog

In general, you swim along the Tsugaru Strait on the tide that flows from the Sea of Japan to the Pacific Ocean, but as you can see from the diagram, the thin lines (A, B, C) are the routes that I mainly supported. But Andy wants to swim the straight line of the bold arrow.

Haruyuki Ishii

Credit: Haruyuki Ishii

Ocean-Navi Routes

Ocean-Navi routes 22 of the 42 swims Ocean-Navi processed. There are now 57-58 swims total for Tsugaru Strait including Andy Donaldson’s recent swim.


Ocean-Navi – TSSA – Independent

Table of Ocean-Navi swims on their website vs. MSF, OWP, possible missing swim for first female see resources section.(1) Orange highlight over 14 hours, Start and Finish times pending. Andy Donaldson’s recent swim not included yet.

TSSA Routes

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