Passage du Gois is a submersible causeway in the Bay of Bourgneuf, linking the island of Noirmoutier to the mainland in the department of Vendée, in France. Twice a day, for an hour or two, the tide goes out and the causeway becomes visible and accessible to traffic. For the rest of the day, it remains flooded under 1.3 to 4 meters of water and cannot be used.

Although causeways such as Passage du Gois exist in other places (there is one in the county of Jindo in Korea), the uniqueness of Passage du Gois lies in its exceptional length - 4.5 km. In the 18th century, the causeway was much longer because the old dikes were farther from the coast.

In the early days, the only way to reach Noirmoutier was by boat. Then the Bay of Bourgneuf gradually silted up and the causeway was formed allowing men and animals to wade through the waters to the island. In fact, the name “Gois” comes from the verb "goiser" which means to walk while wetting one’s shoes. It was in 1701 that the passage connecting the mainland to the island was first mentioned on a map.

This curiosity has existed since the collapse of the plateau which gave birth to the bay of Bourgneuf. Over a thousand years, the two currents from the north and south hitting the bay has resulted in deposition of silt, and that has continually moved before stabilizing, about a century ago to the current location. Later, stabilization work was done to prevent sand from moving and a cobblestone road was laid down. Around 1840, a regular service was provided by cart or on horseback. In 1971, a bridge linking the island to the mainland was built as an alternative route to the island of Noirmoutier.

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Crossing the causeway is considered perilous. Although tide times are precisely marked on either side of the causeway on large signs, the water comes in at an incredible rate and many visitors get caught out every year. Elevated rescue towers are located all along the Passage du Gois for those caught between the tides. One can climb these towers and wait until they are rescued or the tide falls again.

During low tide, hundreds of tourists and locals alike come to walk, cycle or drive across the Gois. The causeway also attracts a lot of shell seekers looking for edible shells on the exposed sand, especially at low spring tides when the vast expanses of sand which are rich in all manner of shell fish are exposed.

Since 1986, an unusual race across the causeway – the Foulées du Gois – is held every year. In 1999 Passage du Gois was also used by Tour de France bicycle race.

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Foulées du Gois 2013, the annual race Photo credit

Looking for shells. Photo credit

One of the several rescue towers along the Passage du Gois. Photo credit

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Sources: Vendee Guide / Wikipedia