Tsugaru Channel 15 miles
The 5th of the Oceans Seven Hokkaido to Honshu.
These currents are one of the strongest in the world. I was sick for the first 4 hours and had to sprint for the next 11.5 hours to beat the current. I finished in 15 hours 31 minutes
This is a crowd-sourced map. Abilities vary, and conditions change. Always assess risks for yourself before getting in.
The sea can get very choppy and currents strong . The even introduced a tunnel to cross it so you don't have to via ferry.