The main objective of the work is to estimate the time period during which wind waves in the coastal zone can be assumed to be homogeneous (stationary). The analysis is based on the data of field measurements in the Black Sea. The methods of spectral, correlation, wavelet and wavelet correlation analysis were used. It was found that, regardless of the wave formation conditions, wave records with a maximum length of up to 12 min can be considered as homogeneous wave field. Experimental estimates are in good agreement with theoretical ones, that suggests their universality for any coastal zone. Revealed interrelations between two successive homogeneous wave records allow applying the concept of a quasi-homogeneous wave field to a record with a length of up to 24 min. It is shown that in the coastal zone of the sea, the loss of homogeneity of the wave field is due to nonlinear wave transformations processes.