The Naruto whirlpools occur along the Shikoku coast of the Naruto Strait, 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 strait. 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 when the sun, earth and moon are lined up. Under ideal conditions, 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 that prospective visitors check the whirlpool schedules on Naruto Uzu no Michi website when planning a trip to Naruto.