The hydrologic cycle is the cycle through which water passes from sea to land, and from land to sea.
Water vapor enters the air through the evaporation of water.
Water vapor in the air eventually condenses and falls as rain, snow, sleet or hail. Water that falls on land collects in rivers which carry it back to the ocean. The return of water to the ocean may be slowed when water becomes trapped in lakes, swamps, or openings in the rocks. However, most water returns to the ocean. It is interesting to consider the events which led to the formation of the world's oceans although the present knowledge is not perfect.