An approach for routine identification of swell and sea in nominally fully developed, omnidirectional, surface water wave energy spectra measured in arbitrary water depth is developed, applied, and discussed. The methodology is an extension of earlier work with deepwater spectra and involves identifying the frequency at which wave steepness is maximized and relating this to the swell separation frequency. The TMA parameterized spectrum is employed to establish a relationship between the two frequencies so that the methodology can be used when wind data are unavailable. The methodology is developed for finite water depth and tested using a dataset that includes both acoustic Doppler current profiler and wave buoy data, recorded simultaneously at the same location. For cases where the sea and swell are clearly, visually distinguishable in the omnidirectional spectra, the new method accurately distinguishes between the two, but it can also be used to identify sea and swell in unimodal spectra.
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