This general overview article presents water as a unique substance, which constantly accompanies people on our globe. The authors described the most important physical (density, boiling point, maximum density temperature, critical temperature, heat of fusion, evaporation heat, specific heat, surface tension, dynamic viscosity, electrolytic conductivity) and chemical properties (pH, solubility) of water. These properties are important for the functioning of soils and both living organisms (microorganisms, plants, animals, humans) as well as inanimate elements of the environment (lithosphere, waterbodies, watercourses, landscape, etc.). The authors presented the polygenetic origin of water (from the emission of volcanic gases, lava, comets, asteroids) and characterised the Earth’s water resources, paying particular attention to the limited quantity and exponentially growing demand for fresh water. This situation was illustrated with the water footprint – an indicator of the amount of fresh water which is used directly or indirectly to produce any natural or artificial thing. The article also discusses the negative aspects of water (floods, tsunamis, water erosion), which have been intensified by ill−considered human activities (deforestation, limitation of soil water retention capacity, etc.) in recent centuries. The authors emphasised the therapeutic properties of water, which can be used to treat various ailments (water massages, steam baths, purifying parameters of mineral and spring waters). The article also mentions the scenic functions of water as a liquid (water scenic parks, geysers, hot springs, waterfalls), solid (glaciers) and gas (fog, clouds, rainbow, halo phenomenon). The authors also mentioned the need to save water both globally and locally. As the deficit of this valuable substance is constantly increasing, it may cause numerous conflicts in the near future, as they already occurred in the past at various intensity.