Hydrosphere (Greek hydro- means "water") in physical geography, describes collective mass of water that is found under, on and over the surface of the Earth.

Water comprising hydrosphere is found in various forms :

under the Earth's surface and in rocks
in biosphere - plants and animals
water covering the Earth's surface in liquid and solid forms (ice, snow)
atmospheric water in clouds and water vapour

Other spheres are :

lithosphere
atmosphere