In this work we consider the evolution of power spectra of waves during a period of one year. Soukissian and Samalekos (2005) have proposed a segmentation method for significant wave height based on determining periods of stability, increase and decrease using time-series techniques. The second segmentation method is based on the mean value over a moving window, and uses a fixed-width band to determine the change-points in the register. We compare both segmentation methods for several spectral characteristics and give a statistical analysis of duration and intensity of sea states in each case.