A hydrosphere (from Greek ύδωρ - hydor, 'water' + σφαίρα - sphaira, 'sphere') in physical geography describes the combined mass of water found on, under, and over the surface of a planet.
The total mass of the Earth's hydrosphere is about 1.4 × 1024 grams, which is about 0.023% of the Earth's total mass. About 2 × 1019 grams of this is in the Earth's atmosphere. Approximately 71% of the Earth's surface, an area of some 361 million square kilometers (139.5 million square miles), is covered by ocean.
