one word [tide]
(ref: here ) cadence, cadence, splashing waves simple droplets become waves crashing, splashing, on the reef, cadence, crisp and salty sweet cadence, cadence, eventide time, defined by water's ride crashing, craving, waves of life cadence of survival's knife cadence, cadence, crisp and sweet back and forth the waves all meet crashing, high and low, the tides cadence soothes and heat subsides cadence, cadence, short and long cacophany of creature song crashing, as the days go by cadence kept and ne'er dry