The whirlpools are caused by the narrowness of the strait, which is only 1.3 kilometers wide.
The name 'Naruto' translates literally to 'roaring gate' or 'roaring channel'.
Water velocity in the strait ranks among the fastest in Japan.
The intensity of the whirlpools follows a 6-hour tidal cycle, peaking twice daily.
The whirlpools are categorized as one of the three major currents in the world alongside the Saltstraumen in Norway and the Seymour Narrows in Canada.
The Naruto Whirlpools are naturally occurring tidal phenomena situated in the Naruto Strait, between Naruto in Tokushima and Awaji Island. These vortices form due to the significant water level differential between the Seto Inland Sea and the Kii Channel during high and low tide cycles. The whirlpools can reach diameters of up to 20 meters during spring tides, making them some of the largest in the world. Water flows through the narrow strait at speeds reaching 20 kilometers per hour. Sightseeing vessels operate from the Naruto side to allow visitors to view the currents from a close proximity. The site is spanned by the Onaruto Bridge, which sits 45 meters above the sea surface.
The 'Uzu-no-Michi' observation walkway built into the lower truss of the Onaruto Bridge.
Consult the official tidal table online before your trip, as the whirlpools are only visible during specific intervals surrounding tide changes.
Choose a sightseeing boat with an underwater viewing deck to observe the currents from below the surface.
Wear a windbreaker, as the spray and high winds on the open deck can be intense.
Do not plan a visit without checking the daily tidal charts, as the whirlpools are completely invisible during slack water periods.
Operations are subject to cancellation during severe weather or high-wave warnings.
Hold onto railings on sightseeing boats; follow crew instructions regarding safety vests and designated standing areas.
