Rare supertide turns ancient Mont Saint-Michel into island ← Related Article Visit The Boston Globe Share on Twitter Share on Facebook Comment on this Scroll to top of page A supertide turned France’s famed Mont Saint-Michel into an island and then retreated out of sight, delighting thousands of visitors who came to see the rare phenomenon. Associated Press People gathered ahead of a high tide, which submerged a narrow causeway leading to the Mont Saint-Michel in France. Associated Press The so-called tide of the century actually happens every 18 years. PASCAL ROSSIGNOL/Reuters A group of people walked on the mud flats at low tide. GUILLAUME SOUVANT/AFP/Getty Images People waited for the wave, named "Mascaret," in front of the abbey church on the top of the Mont-Saint-Michel. PASCAL ROSSIGNOL/Reuters The incoming high tide surrounded the 11th century abbey off France's Normandy coast. GUILLAUME SOUVANT/AFP/Getty Images An even higher tide was predicted for Saturday night. PASCAL ROSSIGNOL/Reuters Tourists walked through retreating waters with a bay guide. CHARLY TRIBALLEAU/AFP/Getty Images Surfers took to the "Mascaret" wave in Pontaubault, in Northwestern France. GEOFF CADDICK/AFP/Getty Images A surfer took the wave of the tidal bore, called Severn bore, on the River Severn in Southwest England.