Naruto’s whirlpools are formed through the interaction of tidal currents with the local topography. Spring tides funneled through the vee-shaped strait can reach speeds of 20 kph as they rush between the Pacific Ocean and the Inland Sea. Below the surface, there’s also a deep depression that helps bring the tides together in such a way that it generates vortices 20 meters in diameter.
In normal times, the whirlpools are a significant tourist attraction during the springtime. Travelers can view them from tour boats, helicopters, and from the Onaruto Bridge. (Image credits: whirlpools – Mainichi/N. Yamada, Discover Tokushima; artwork: Hiroshige; via Mainichi; submitted by Alan M.)