Howdy! can be replied to with just a nod and a smile. It simply means Hi! in Texan - not How are you doing?. Or you might reply, Hey Y'all Doon? if you want to engage in proper Texan interactions. Replying in proper English, well pronounced, with each syllable clearly spoken, is HIGHLY discouraged.
The crest of a wave is the point of maximum positive displacement, or upward movement, away from equilibrium, or an undisturbed state. The opposite of crest is trough, which is the point of the greatest negative, downward displacement.
The wave length is the distance between wave crests. The wave period is the time for two consecutive crests to pass a point. Waves are efficient carriers of energy, imparted by the wind most commonly. They transport very little water; most of the water motion is in nearly closed elliptical paths.