When you throw a stone into a pond, it creates a series of ripples, or waves, that propagate outward in concentric circles until they encounter obstacles.
Out in the world, waves are generated when forces such as wind and tide disturb the water’s surface.
The wavelength of a wave in water can be determined by measuring the distance from the crest of one wave to the crest of the next wave.
The frequency of waves in water can be determined by counting the number of waves that reach their peak or crest at a specific point over a set period of time.
The amplitude of a wave is often approximated by measuring half the vertical distance from the top of a wave (the crest) to the bottom of a wave (the trough). However, strictly speaking, it should be the distance from the undisturbed surface level of the water to the next crest or trough. This is an approximation because it assumes that waves are symmetrical and that the undisturbed water level is midway between the crest and the trough.
The direction of travel of water waves can typically be easily determined by observing their movement.
The energy carried by waves at the beach becomes evident when you experience their force while swimming, for instance, being toppled over by a wave.