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.