A gravity separator S separates a liquid phase O and a gas phase G from a multiphase fluid mixture E. The gravity separator comprises a collector 1 for collecting the liquid phase O, an outlet 8 for extracting the gas phase G and a draining circuit 3 coupled to the collector 1 for draining the liquid phase O out of the separator. The gravity separator S further comprises a floating assembly 2 coupled to the collector 1. The floating assembly is arranged to float at an interface GLI between the liquid phase and the gas phase so that the collector is positioned in the multiphase fluid mixture present in the gravity separator S for collecting substantially the liquid phase O.