The Xynthia storm, which occurred on the night of February 27-28, 2010, was a major disaster, with 47 victims and estimated damages between 2.1 and 2.5 billion of euros. A compilation of numerous reports and publications shows some conflicts between expertise and political decisions, between economic development and population security, between memory and forgetting... The community of La Faute-sur-Mer was particularly affected with 29 victims. Transcripts of the hearings of the trials of 2014 and 2016 give an in-depth investigation of the main failures of flood risk mitigation. The storm Xynthia has been a source of major improvements for flood risk prevention tools, in particular the implementation of an alert system for marine submersions, the creation of a "Rapid Submersion Plan", and a new National Observatory for Natural Hazards.We conclude by emphasizing that the public should be better involved in flood risk prevention, with important issues related to risk education, vulnerability and resilience of society.