Breaking and grouping of surface waves are observed at Bohai Sea. The measurement system mainly consists of two hydrophones and a pressure sensor underwater. The broadband hydrophones are able to track breaking waves by passive detection of naturally generated ambient sound of breaking. The breaking criterion in terms of Sound Spectrum Level (SSL) is chosen to identify the breaking waves. The simultaneous wave elevation signals are measured with the pressure sensor, to get the wave group information. Special emphasis is put on the portable data acquisition system based on virtual instrumentation, which makes the in situ measurement convenient and user-friendly. By use of the field data, a wave age dependent model for wave breaking probability is reanalysed, and the result shows a good agreement; moreover, the relationship between breaking and grouping is tentatively investigated, the results are in agreement with the earlier findings that breaking was correlated strongly with group structure and occurred most commonly in the center of a group.
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