The rain drop can run off and reach the ocean in a river. It can evaporate and become a cloud again and rain again and again. The rain drop can also be absorbed into the ground and end up being taken into a plant and then be respired into the air to become a rain drop again. Or the rain drop can sink into the earth and become part of an underground aquifer and eventually flow into a river and into the ocean. One other path would be for the rain drop to fall in the mountains and turn to ice and end up as part of a glacier and eventually flow into the ocean if it is in Alaska or somewhere that glaciers flow into the ocean.