The Naruto whirlpools occur on the Shikoku side of the Naruto Straight, and are created by the large volumes of water moving between the Seto Inland Sea and the Pacific Ocean between high and low tide, combined with the unique underwater geography of the narrow straight.
According to the change of tides, the whirlpools occur roughly every six hours and can typically be seen once in the morning and once in the afternoon for an hour or two. The whirlpools vary in size, depending on the intensity of the tides. They tend to be larger in summer than in winter, and are largest during spring tides, which occur every two weeks.
If all factors play together favorably, whirlpools of up to 20 meters in diameters can be observed. On the other hand, there is not much to see on calm days or outside of the peak times. Therefore, it is of great importance to check the whirlpool schedules (see links below) before making a visit to Naruto.
The Wonder Naruto tour boat
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Onaruto Bridge
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The whirlpools are not dangerous to boats, and are best viewed from sightseeing boats which get right up next to and among the whirlpools. There are two companies that run tours to the whirlpools from nearby piers on Shikoku and one from Awaji Island on the opposite side of the straight.
On the Shikoku side, Uzushio Kisen operates small boats with water level decks from a pier just outside Naruto Park. A little bit further away is the pier of Uzushio Kankosen, which operates the "Aqua Eddy" (medium sized boats with two decks and underwater windows) and "Wonder Naruto" (large sized boats with two decks) to the whirlpools.
As the whirlpools are best viewed from a higher vantage point, it is recommended to take a "Wonder Naruto" boat tour which offers the best views from its upper first-class deck at an additional charge. Boat tours by both companies last 20 to 30 minutes with two departures per hour.
Uzu no Michi
The next best views are from Uzu no Michi, an enclosed walkway that extends under the Onaruto Bridge and overlooks the whirlpools. The walkway's observation room sits 45 meters above the whirlpools below which can be seen through glass windows set in the floor.
Naruto Park (Naruto Koen), the park encompassing the attractions around the whirlpools, also has a number of walking trails and viewpoints set around it with views of the whirlpools and Onaruto Bridge. The best views of the swirling water are from the Senjojiki Observatory. Another viewpoint, Eska Hill, is accessible via a 68 meter long, paid escalator, but its restaurants and shops appear rather run down.
Also found in the park, the Onaruto Bridge Museum Eddy is devoted to the construction of the bridge, the straight and its whirlpools. And last but not least, nearby stands Japan's largest museum, the Otsuka Museum of Art, which displays nothing but reproduced Western Art.
Naruto Park with Eska Hill as seen from the Onaruto Bridge Museum
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