A method for detecting a floating layer on a surveillance area of a sea surface, a site of interest being located in or at a rim of the surveillance area, the method comprising at least the steps of: a) satellite measurement of a returned radar signal, the radar signal being transmitted by a satellite toward the sea surface of the surveillance area; b) recognition of at least one swell profile of the sea surface, based on the satellite measurements; c) identification of fluid properties corresponding to the recognized swell profiles; and d) emission of a warning when the fluid properties identified for one of the recognized profiles correspond to a sea surface comprising elements that are undesirable for the site of interest; wherein, in step b), distinctive boundaries of swell profile are further recognized in the surveillance area, the distinctive boundaries corresponding to pronounced localized variations in levels of the satellite measurements; the at least one recognized swell profile corresponding to a set of measurements whose level varies according to a same wavelength of the recognized swell profile and a same amplitude, the set of measurements being delimited at least in part by the recognized distinctive boundaries; characterized in that: in c), the fluid properties of the at least one recognized swell profile are identified by: - determining a volume fraction as a function of: ∘ a damping coefficient of amplitude of the swell at the distinctive boundaries, ∘ a number of waves at the distinctive boundaries, determined from the wavelength of the recognized swell profile, - identifying the fraction among the predefined volume fractions that is closest to the determined volume fraction, the predefined volume fractions being associated with predetermined fluid properties; and - associating the recognized swell profile with the predetermined fluid properties of the predefined volume fraction identified as being closest to the determined volume fraction. a) satellite measurement of a returned radar signal, the radar signal being transmitted by a satellite toward the sea surface of the surveillance area; b) recognition of at least one swell profile of the sea surface, based on the satellite measurements; c) identification of fluid properties corresponding to the recognized swell profiles; and d) emission of a warning when the fluid properties identified for one of the recognized profiles correspond to a sea surface comprising elements that are undesirable for the site of interest; - determining a volume fraction as a function of: ∘ a damping coefficient of amplitude of the swell at the distinctive boundaries, ∘ a number of waves at the distinctive boundaries, determined from the wavelength of the recognized swell profile, ∘ a damping coefficient of amplitude of the swell at the distinctive boundaries, ∘ a number of waves at the distinctive boundaries, determined from the wavelength of the recognized swell profile, - identifying the fraction among the predefined volume fractions that is closest to the determined volume fraction, the predefined volume fractions being associated with predetermined fluid properties; and - associating the recognized swell profile with the predetermined fluid properties of the predefined volume fraction identified as being closest to the determined volume fraction.