Waves are formed as a result of the constant friction between water and wind. If a wind is blowing over the water surface, it carries away particles of water with it. The water starts moving in this way. Therefore, the distance between the ‘wave crests’ is determined by the wind. A constant wind gives rise to long, soft waves, which are also known as ‘groundswell’; a high wind, on the other hand causes small and strong waves, the typical ‘motion of the sea’. Unlike the tsunamis, these waves occur only at the surface of the water. At a depth of a few metres, the waves do not create any disturbance.