Unusually high and low tides due to the every 18 years full-moon-perigee coöccurance, coupled with the natural topography that causes some of the most extreme tides in the world, Mont Saint-Michel in France, temporarily became both fully attached and fully detached from mainland today.

The supertide phenomenon occurs only every 18 years when several astronomical factors coincide
Crowds gathered on the causeway were pushed back by the advancing tide
Picture: AP

A woman walks on the sand at low tide around the Mont Saint-Michel 11th century abbey off France’s Normandy coast. At Mont Saint-Michel, where some of the biggest tides in the world occur, visitors have gathered to watch the tide disappear out of sight, exposing areas of beach and rock visible only every 18 years
Picture: REUTERS/Pascal Rossignol