Naruto Whirlpools

The Naruto Strait is only about 1.3 kilometres wide, and every six hours the Pacific and the Inland Sea have to change places through it. The level difference between the two sides can reach a metre and a half, the current runs at up to about 20 kilometres an hour, which is the fastest in Japan, and where the fast water shears past the slow water at the edges you get the whirlpools. At spring tides the largest reach twenty metres across and hold together for a few seconds before collapsing.

Timing is everything and most disappointed visitors got it wrong. The peak happens roughly twice a day and shifts by about fifty minutes each day, so a fixed itinerary will not work. Check the published tide schedule and aim for the window around maximum flow. Around the new and full moon in spring and autumn is when the tidal range is greatest and the whirlpools are worth the trip. At neap tide, in between, you will see fast water and a few swirls.

Two ways to see it. Sightseeing boats run out from Fukura port on the Awaji side and from Kameura on the Tokushima side, and they take you right to the edge of the vortices, which is loud, wet and the better experience. Or walk the Uzu-no-Michi, a 450-metre corridor built into the underside of the Onaruto Bridge with glass panels in the floor 45 metres above the water. Standing on the glass and looking straight down into a rotating hole in the sea is a strange sensation, and it works in weather that cancels the boats.

Wakame from these currents is a local speciality and it is genuinely different, worth eating while you are here.