The hydrosphere is the part of a planet that's made of water. Oceans, rivers, lakes, and clouds are all typically included in the hydrosphere.
The watery parts of our planet, including vapor that hovers above the Earth's surface and water that's underground, make up its hydrosphere. Most of this water is salty, found in oceans, seas, estuaries, and other salty spots. Some of it is frozen into ice caps and permanent snow cover. Hydrosphere combines the Greek root hydro-, "water," and sphere, "globe, cosmos, or space," from the Greek sphaira, "globe or ball."