A method, comprising: predicting, based on a multidimensional shot gather for a target structure, and using a receiver-side propagation, first data representing a receiver-side multiple using a multidimensional model of a layer in which the receiver-side multiple occurs, the multidimensional model of the layer being a three-dimensional or four-dimensional model of the layer; predicting, based on said multidimensional shot gather, and using a first source-side propagation, second data representing a first source-side multiple using the multidimensional model; predicting, based on the first data, and using a second source-side propagation, third data representing a second source-side multiple using the multidimensional model; producing modified survey data by performing a subtraction of the predicted data representing the respective multiples from the multidimensional common shot gather, the modified survey data comprising a multidimensional common receiver gather; the method providing a water-layer demultiple, DWD, technique which produces DWD output data from input measured survey data; characterized in that the DWD technique performs a simultaneous adaptive subtraction using equation: Dout = Din − fS * S − fR * R − fSR * SR, wherein: - Din represents the input measured survey data; - Dout represents the DWD output data; - R, S and SR represent the first, second and third data, respectively; - * denotes convolution; - fS, fR and fSR are subtraction operators used in the simultaneous adaptive subtraction; and - constraints are provided on the operators fS, fR and fSR to set approximately equal operators fS and fR and to set the operator fSR to be approximately a polarity-reversed version of the operators fS and fR. predicting, based on a multidimensional shot gather for a target structure, and using a receiver-side propagation, first data representing a receiver-side multiple using a multidimensional model of a layer in which the receiver-side multiple occurs, the multidimensional model of the layer being a three-dimensional or four-dimensional model of the layer; predicting, based on said multidimensional shot gather, and using a first source-side propagation, second data representing a first source-side multiple using the multidimensional model; predicting, based on the first data, and using a second source-side propagation, third data representing a second source-side multiple using the multidimensional model; producing modified survey data by performing a subtraction of the predicted data representing the respective multiples from the multidimensional common shot gather, the modified survey data comprising a multidimensional common receiver gather; the method providing a water-layer demultiple, DWD, technique which produces DWD output data from input measured survey data; characterized in that the DWD technique performs a simultaneous adaptive subtraction using equation: Dout = Din − fS * S − fR * R − fSR * SR, wherein: - Din represents the input measured survey data; - Dout represents the DWD output data; - R, S and SR represent the first, second and third data, respectively; - * denotes convolution; - fS, fR and fSR are subtraction operators used in the simultaneous adaptive subtraction; and - constraints are provided on the operators fS, fR and fSR to set approximately equal operators fS and fR and to set the operator fSR to be approximately a polarity-reversed version of the operators fS and fR.