Chugoku

Chugoku is the westernmost region of Honshu's main landmass, and its southern coast faces the Seto Inland Sea — Setonaikai in Japanese — a 450 km corridor of sheltered water enclosed between Honshu to the north and Shikoku and Kyushu to the south, studded with more than 3,000 islands. The tidal character of the Seto Inland Sea is the defining physical fact of this coast. The sea is connected to the Pacific at its eastern end through the Kii and Naruto Channels and at its western end through the Kanmon Strait near Kitakyushu, and because these two openings have slightly different tidal phases, the sea acts as a resonant basin. The resulting tidal currents between islands and through narrow straits routinely exceed several knots on spring tides — the Naruto whirlpools at the eastern entry, where Tokushima Channel narrows to 1.3 km, produce the most dramatic surface expression, with vortices up to 20 m in diameter on large spring tides. In Hiroshima Bay specifically, mean range runs roughly 1.5 to 2.0 m, semidiurnal, with two roughly equal highs and two roughly equal lows per day. The most famous single tide-dependent landmark in Japan sits within this region: the O-torii gate of Itsukushima Shrine on Miyajima Island, 20 km southwest of Hiroshima city. The gate stands 16 m tall in the tidal flat off the shrine's waterfront. At high water the gate appears to float on the sea surface, surrounded by water with no visible footing — the image that appears on postcards and in every photography guide to Japan. At low water, the tidal flat is exposed for 200 to 300 m in front of the gate, and visitors wade out to stand at its base on the sandy bottom. The difference between these two states is the tide: the same gate, the same location, two completely different visual experiences separated by roughly six hours of tidal cycle. The Japan Meteorological Agency and Japan Coast Guard maintain the official Hiroshima and Miyajima tide records. Open-Meteo Marine drives the gridded predictions on TideTurtle pages for this region.