The waves on the sea surface are not a simple wave train but a complicated random surface. It is impossible to give a simple amplitude and frequency for a system as complex as this. Instead, significant wave height, the mean height of the highest third of the waves, is used to describe how large the waves are, and the peak period, the time between the dominant or most energetic waves, is used as a measure of frequency. On average, there will be a wave twice the significant wave height every three hours. Eventually, the energy put into the sea by the wind will be balanced by the loss of energy, mainly through waves breaking.
Waves can travel thousands of kilometres from the point of generation.
They have a much narrower range of periods and are almost regular wave trains. Because no more energy is put into them, none is dissipated by breaking, and they continue across the ocean until they hit the land. Because different frequencies travel at different speeds, as swell travels across the ocean it separates into its individual components. So the significant wave height and peak period of the swell are set by the wind speed, duration and fetch from the storm that generated them. The longer the wind blows, the longer the wavelength of the predominant waves in the wind-sea.