Due to the narrowness between the Japanese islands of Shikoku and Awaji, the tidal range pushes the water at up to 20 km/h - the third fastest tidal current in the world. This is how the huge Naruto whirlpools with diameters of up to 20 meters are created under the 1.6 km long Naruto Bridge that connects the islands.
Once you have checked the tide schedule, you should arrive in Naruto at the right time so that you can take a boat close to the whirlpool. As soon as the water levels of the Pacific and Seto Inland Seas begin to equalize, the eddies disappear again. you have two chances in daylight. The whirlpools can be also viewed from the bridge, where is a beautiful observation point 450 meters away from the mainland is located. Here glass panes are embedded in the floor, through which you can look directly 45 meters deep into the thundering whirlpools - not for the faint of heart. Some even do tests of courage here by lying down on the glass.
We lived in Takamatsu in the north of Shikoku Island and on the Japanese Set Inland Sea. To get to the Naruto Whirlpool by public transport, we would have had to change four times and it would have taken us five hours. So we rented a small car. For rental cars in Japan you need a translation of the driver's license into Japanese - we had it with us and were pleasantly surprised at the local rental company when the functions of the car were explained to us very carefully with display boards. However, we already had the impression that we were looked a little worried afterwards when we left for Naruto. The relief of the car rental company seemed all the greater when we returned safely from the excursion in the evening - driving a car in Japan is far less problematic than in some European countries ;-) :-)