The science and engineering application of water or other fluids. The study of liquid water (or other liquids, e.g. ammonia, methane, etc. in exotic environments), including its physical and chemical properties, geographical distribution, fluid dynamics, interaction with the surrounding landforms (rivers, flooding, erosion, etc.), engineering for the creation and maintenance of rivers, canals, lakes, dams, seas and oceans, and the water cycle in ecology and planetology, and the part that water plays in making terraformed planets and megastructures habitable to biological organisms.