When will the waves at the shore be the smallest and calmest?

When the wind is not blowing

Explanation:

Wave moves from one place to another when a force is applied by the wind on the surface of water. So, when a tide comes or recedes then it means a force is applied by wind, movement of earth etc.

Therefore, a sound will also produce due to the movement of these waves and also there will be some height of the waves.

Hence, this means that upwelling of wave, receding or coming of tide will be high and not calm.

Whereas when no wind is blowing then water will move very slightly. Therefore, in that case the waves at the shore be the smallest and calmest.