Paris Underwater is an in situ adaptation of United Land project representing the last ten years, the planet partly covered by the sea and surrounded by ice.

François Ronsiaux invests with, of shifting light effects devices, and processing of public and private lighting, a neighborhood of the 20th district in order to achieve a light installation to simulate the city of Paris in the abyss after a hypothetical rising waters.

Residents and shopkeepers are involved and invited to join the project by transforming their personal lighting time Nuit Blanche 2015 .