All of the Earth's water, including surface water (water in oceans, lakes, and rivers), groundwater (water in soil and beneath the Earth's surface), snowcover, ice, and water in the atmosphere, including water vapor.
The water vapor in the earth's atmosphere.
All the water on the surface of the earth, including oceans, lakes, glaciers, etc.: water vapor, clouds, etc. may be considered part of the atmosphere or of the hydrosphere.
The waters of the earth's surface as distinguished from those of the lithosphere and the atmosphere.