Correction of sea surface state

A wavefield based on the actuation of at least one source in a body of water used in a seismic survey, also using a plurality of receivers, and a sea surface state at the source at one of a plurality of shot points is determined. The up-going and down-going wavefields may be mathematically separated, and the source-side effects in the up-going wave may be determined. Constant receiver and constant channel ensembles may be cross-correlated, and based on this data may be statistically filtered and a surface consistent time correction extracted to apply to the plurality of shot points. The sea surface state may be determined by comparing an up-going portion of the measured wavefield to an up-going portion of a different measured wavefield. A computing system calculates cross-correlations at a constant channel between consecutive shot points, at a constant channel within a shot point between consecutive channels, and within a constant receiver between consecutive shot points, and corrects the sea surface state. The ensemble of source units, channels and receivers may include a constant distance from the source to a sea surface, and constant channel and receiver directions.